Map Viewer allows you to explore data in various ways through a variety of smart mapping styles. When you style map layers in Map Viewer, the nature of the data determines the default styling options. You can experiment with color ramps, line weights, transparency, symbols, and other graphic elements, and see your choices reflected immediately on the map.
The styling options described below are available for visualizing features according to numeric values in your data.
Counts and Amounts (color)
If you have numeric data, you can distinguish features using graduated colors to reflect a count or an amount. Different types of color ramps can be used—for example, a simple light-to-dark color ramp is good for showing low-to-high data values such as age, income, or ratio. Color ramps can be applied to points, lines, and polygons. For example, you can use a light-to-dark color ramp to represent the market value of parcels from high to low.
To style counts and amounts using color, do the following:
- Follow the first five steps of Apply a style.
- In the Styles pane, click the Counts and Amounts (color) style if necessary and click Style options.
- Optionally, do the following:
- Choose a theme for the color ramp. A number of color themes are available. Each color theme can tell a different story by matching colors to data in different ways.
- If the data isn’t normalized or standardized, choose an attribute field from the Divided by drop-down menu to turn the raw data into rates or percentages. Examples of normalized data include x per capita, y per square kilometer, or a ratio of x to y. Raw counts, by comparison, are better visualized with colors after they are standardized.
- Click the color ramp under Symbol style and specify the color ramp settings to use a different color ramp or to change other graphic parameters such as stroke weights and colors. For more information, see Use style options.
- In the Style options pane, click Invert color ramp
to invert, or flip, the colors in the color ramp. - Adjust the bounding handles along the color ramp to change how it is applied to the data. You can either drag the handle or click the number next to the handle and type a value. Experiment with the position of the handles and use the histogram and calculated average option
to understand the distribution of the data to fine-tune the message of the map.Tip:
Click Magnify slider
to enlarge the details in the histogram. To return to the original slider positions at any time, click Reset slider positions 
. - Turn on the Show features with no value toggle button to draw locations with missing data on the map, and optionally specify a style and label to represent those values.
- Turn off the Include in legend toggle button to hide the color ramp in the legend.
- Turn on the Classify data toggle button and choose the classification method and the number of classes to further generalize the map, or if you're using standard deviation, choose the interval. You can also click the individual color chips in the classification legend to manually edit the symbols and labels for the classes in the map legend.
- Click Transparency by attribute, turn on the Set transparency based on attribute values toggle button, and specify the transparency settings. You can only use this option if you have numeric or date data associated with the locations. For example, if the layer contains population data, you can adjust the transparency of each location proportionally to its population.
- If you are mapping point symbols, you can rotate symbols based on a second numeric attribute. For example, the color of the points depicts air temperature at weather stations, while the rotation of the points depicts humidity. The default symbol is round, which doesn't depict rotation well. It is best to choose a different shape. Click Rotation by attribute to rotate symbols, and specify the rotation settings.
- Click Done when you are finished customizing the style, or click Cancel to return to the Styles pane without saving your choices.
Counts and Amounts (size)
This map style uses an orderable sequence of sizes to represent numeric data or ranked categories. Points, lines, and areas can all be drawn using this style. Polygon features are displayed as proportional points over polygons. These proportional symbol maps use an intuitive logic in which larger symbols equate to larger numbers. Adjust the size of the symbols to clarify the story you’re telling. For example, you can use proportional symbols to show the annual average daily traffic in a city.
To style counts and amounts by size, do the following:
- Follow the first five steps of Apply a style.
- In the Styles pane, click the Counts and Amounts (size) style if necessary and click Style options.
- Optionally, do the following:
- Choose a theme for the symbols. Several themes are available. Each theme can tell a different story by matching different-sized symbols to data in different ways.
- If the data isn’t normalized or standardized, choose an attribute field from the Divided by drop-down menu to turn the raw data into rates or percentages. Examples of normalized data include x per capita, y per square kilometer, or a ratio of x to y. Raw counts, by comparison, are better visualized with colors after they are standardized.
- Click the symbol under Symbol style and specify the settings for the styling of proportional symbols (color, stroke, and opacity). For more information, see Use style options.
- In the Style options pane, click Invert size ramp to invert, or flip, the symbol size order.
Note:
By default, higher values are drawn with larger symbols and lower values are drawn with smaller symbols. Clicking Invert size ramp allows you to reverse this pattern.
- Adjust the bounding handles along the histogram to change how the proportional symbols are applied to the data. You can either drag the handle or click the number next to the handle and type a value. All values above the upper handle are drawn with the same largest symbol. Values below the lower handle are displayed with the same smallest symbol. The remaining values are drawn with a proportional sequence of sizes between the two bounds. Experiment with the position of the handles and use the histogram to see the distribution of the data to fine-tune the message of the map.
Tip:
Click Magnify slider
to enlarge the details in the histogram. Click Reset slider positions to return to the original slider positions at any time. - For Size range, keep the default size range or specify a custom range (in pixels) by adjusting the slider handles or clicking the default values and providing new values. Keep the Adjust size automatically check box checked to optimize the symbols for the current map zoom level and automatically adjust them at other zoom levels.
- If you are mapping data associated with polygons, click the symbol under Symbol style and adjust the fill and stroke properties of the polygons. For more information, see Use style options.
Tip:
By default, polygon feature symbols in the layer—for example, county boundaries—are shown on the map under the proportional symbols. To keep this setting, leave the Show background symbol toggle button turned on and optionally customize the symbol style for the background features, such as adjusting the transparency or changing the outline color. To hide the background symbols in the layer—for example, if you don't want to see county boundaries under the proportional symbols—turn off the Show background symbol toggle button.
- Turn on the Show features with no value toggle button to draw locations with missing data on the map, and optionally specify a style and label to represent those values.
- Turn off the Include in legend toggle button to hide the size ramp in the legend.
- Turn on the Classify data toggle button and choose the classification method and the number of classes to further generalize the map, or if you're using standard deviation, choose the interval. You can also click the individual color chips in the classification legend to manually edit the symbols and labels for the classes in the map legend.
Note:
These options aren't available with the Color and Size, Types and Size, or Predominant Category and Size styles.
- Click Transparency by attribute, turn on the Set transparency based on attribute values toggle button, and specify the transparency settings. You can only use this option if you have numeric or date data associated with the locations. For example, if the layer contains population data, you can adjust the transparency of each location proportional to its population.
- If you are mapping point symbols, you can rotate symbols based on a second numeric attribute. For example, the size of the points depicts air temperature at weather stations, while the rotation of the points depicts humidity. The default symbol is round, which doesn't depict rotation well. It is best to choose a different shape. Click Rotation by attribute to rotate symbols, and specify the rotation settings.
- Click Done when you are finished customizing the style, or click Cancel to return to the Styles pane without saving your choices.
Dot Density
Use the Dot Density style to visualize the distribution of one numeric attribute or to compare multiple numeric attributes using different-colored dots. With this style, each dot represents a count of something or someone, such as citizens, sales, or crimes. The Dot Density style works well for layers with polygon features associated with counts or totals that share a common unit of measurement, such as people, houses, incident reports, total dollars, and more. For example, you can use this style to show the concentration of unsheltered homeless people compared to sheltered homeless people in a city, or the distribution of population by race across the United States.
When you apply dot density styling to a layer, you select the quantity represented by each dot—for example, one dot represents 20 trees. You can also customize the legend and color ramp, and specify other settings to fine-tune the style.
To style using dot density, do the following:
- Follow the first five steps of Apply a style.
- Repeat the previous step to select additional numeric attributes.
Each attribute should represent a distinct category related to the first attribute and should have the same unit of measure.
- Click the Dot Density style and click Style options.
- Optionally, do the following:
- Click the color ramp under Symbol style and change the settings. To customize the color or transparency of any of the categories individually, click the colored symbol next to the category in the list. For more information, see Use style options.
- Click a dot category label, type a new label, and press Enter.
- Drag a category up or down in the list.
- In the Dots represent text box, specify what each dot represents—for example, people, trees, or houses.
- For Dot value, use the slider to specify a value that each dot represents. You can also click the dot value above the slider, type a value, and press Enter.
- Optionally, do the following to fine-tune the dot display:
- By default, polygon feature symbols in the layer—for example, county boundaries—are shown on the map under the dots. Leave the Show background symbol toggle button turned on to keep this setting, and optionally customize the symbol style for the background features, such as adjusting the transparency or changing the outline color. To hide the feature symbols in the layer—for example, if you don't want to see county boundaries under the dots—turn off the Show background symbol toggle button.
- By default, the dot value varies according to the map scale; zooming in on the map decreases the dot value and zooming out increases it. Turn off the Vary dot value by scale toggle button to keep the dot value the same regardless of map scale.
- By default, when more than one category is present in an area, the colors representing those categories are blended for the area. Turn off the Blend overlapping colors toggle button to prevent blending of overlapping colors.
- Click Done when you are finished customizing the style, or click Cancel to return to the Styles pane without saving your choices.
Color and Size
With this style, you choose one or two numeric attributes in the data and specify both the color and the size of point symbols on the map. This is a good style to use to show count information (size) shaded by a rate (color)—for example, the number of people with no health insurance shaded by the percentage of the population that is uninsured. The Color and Size style is also useful for mapping a single attribute in the data using different colors and proportional symbol pairs to show values that are above and below a key value—for example, where childhood obesity rates are above and below the national average.
Style one attribute
To style one attribute using color and size, do the following:
- Follow the first five steps of Apply a style.
- Click the Color and Size style and click Style options.
- From the first drop-down menu, choose a theme. Each theme can tell a different story about the data.
For example, choose the Above and below theme to show where values are above and below a given value, such as above- and below-average traffic levels.
- Optionally, do the following:
- If the data isn’t normalized or standardized, choose an attribute field from the Divided by drop-down menu to turn the raw data into rates or percentages. Examples of normalized data include x per capita, y per square kilometer, or a ratio of x to y. Raw counts, by comparison, are better visualized with colors after they are standardized.
- If you chose Above and below for the theme, select a symbol pair from the Symbol pair drop-down menu to use different symbols, such as up and down arrows for the above and below values. Alternatively, to use the same symbol in different colors for all values, select Single symbol and select a symbol—for example, squares. For Color scheme, select Continuous to apply a smooth and gradual color ramp, or select Binary to group the data into two distinct colors.
- Click the color ramp under Symbol style and specify the color ramp settings to choose a different color ramp or to change other graphic parameters such as stroke weights and colors. For more information, see Use style options.
- In the Style options pane, click Invert color ramp to invert, or flip, the colors in the color ramp.
- Adjust the bounding handles along the histogram slider to change how the color ramp and symbols are applied to the data. You can either drag the handle or click the number next to the handle and type a value. Experiment with the position of the handles and use the histogram and calculated average option to understand the distribution of the data to fine-tune the message of the map.
Tip:
To enlarge the details in the histogram, click Magnify slider
. To return to the original slider positions at any time, click Reset slider positions . - For Size range, keep the default size range or specify a custom range (in pixels) by adjusting the slider handles or clicking the default values and providing new values. To optimize the symbols for the current map zoom level and automatically adjust them at other zoom levels, keep the Adjust size automatically check box selected.
- If you are mapping data associated with polygons, click the symbol under Symbol style and adjust the fill and stroke properties of the polygons. For more information, see Use style options.
Tip:
By default, polygon feature symbols in the layer—for example, county boundaries—are shown on the map under the proportional symbols. To keep this setting, leave the Show background symbol toggle button turned on and optionally customize the symbol style for the background features, such as adjusting the transparency or changing the outline color. To hide the background symbols in the layer—for example, if you don't want to see county boundaries under the proportional symbols—turn off the Show background symbol toggle button.
- Turn on the Show features with no value toggle button to draw locations with missing data on the map, and optionally specify a style and label to represent those values.
- Turn off the Include in legend toggle button to hide the color ramp in the legend.
- Click Transparency by attribute, turn on the Set transparency based on attribute values toggle button, and specify the transparency settings. You can only use this option if you have numeric or date data associated with the locations. For example, if the layer contains population data, you can adjust the transparency of each location proportionally to its population.
- If you are mapping point symbols, you can rotate symbols based on a second numeric attribute. For example, the color of the points depicts air temperature at weather stations, while the rotation of the points depicts humidity. The default symbol is round, which doesn't depict rotation well. It is best to choose a different shape. To rotate symbols, click Rotation by attribute and specify the rotation settings.
- Click Done when you are finished customizing the style, or click Cancel to return to the Styles pane without saving your choices.
Style two attributes
To style two attributes using color and size, do the following:
- Follow the first five steps of Apply a style.
- Repeat the previous step to select a second attribute or Arcade expression.
Tip:
The first attribute uses color and the second attribute uses different symbol sizes. Switch the order of the attributes by dragging the second attribute to the top of the attribute list.
- Click the Color and Size style and click Style options.
- Define settings for Counts and Amounts (color) (first attribute) and Counts and Amounts (size) (second attribute).
- Click Done when you are finished customizing the style, or click Cancel to return to the Styles pane without saving your choices.
Compare A to B
This style allows you to map the ratio between two numbers and express that relationship as a percentage, simple ratio, or overall percentage. For example, you can map the number of people currently employed as a percentage of the number of employed people in the past year to observe the unemployment trend.
To style ratios, do the following:
- Follow the first five steps of Apply a style.
- Repeat the previous step to select a second attribute or Arcade expression.
- Click the Compare A to B style and click Style options.
- Optionally, do the following:
- Click the color ramp under Symbol style and specify the color ramp settings to choose a different color ramp or change other graphic parameters such as stroke weights and colors. For more information, see Use style options.
- In the Style options pane, click Invert color ramp to invert, or flip, the colors in the color ramp.
- Select an option from the Labels drop-down menu to change labels for the legend and the histogram. You can show the ratio of A to B, show A as a percentage of A and B, or show A as a percentage of B.
- Click Equal values to center the histogram on equal values, or click Average values to center on the average value.
- Adjust the bounding handles along the color ramp to change how colors are applied to the data. You can either drag the handle or click the number next to the handle and type a value. Experiment with the position of the handles and use the histogram next to the color ramp to see the distribution of the data to fine-tune the message of the map.
Tip:
Click Magnify slider
to enlarge the details in the histogram. - Turn on the Show features with no value toggle button to draw locations with missing data on the map, and optionally specify a symbol style and label to represent those values.
- Turn off the Include in legend toggle button to hide the color ramp in the legend.
- If you are mapping point symbols, you can rotate symbols based on a second numeric attribute. For example, the color of the points depicts air temperature at weather stations, while the rotation of the points depicts humidity. The default symbol is round, which doesn't depict rotation well. It is best to choose a different shape. Click Rotation by attribute to rotate symbols, and specify the rotation settings.
- Click Done when you are finished customizing the style, or click Cancel to return to the Styles pane without saving your choices.
Predominant category
This map style is useful if a layer contains multiple related attributes that you want to compare and show which attribute is predominant—that is, has the highest value—and the degree of its predominance compared to the other attributes in the layer. For example, you can use this style to see the predominant ethnic population in each census tract in Los Angeles, California, and how much higher the predominant population is compared to the others.
To use the Predominant category style, choose 2 to 10 numeric attributes with the same unit of measure (for example, United States dollars), each representing a distinct category (for example, 2006, 2007, 2008, and 2009) related to the subject of the map (for example, per capita personal income by county). Each attribute is drawn with a different color—for example, red for 2006 and blue for 2007—defined by the color ramp applied to the layer or by colors you apply to the individual attribute categories.
This style uses transparency to show the relative strength of the predominant attribute for each feature in the layer. The strength, or degree, of predominance is calculated as a percentage of the total value of all the attributes for a given feature. Generally, the higher the transparency (that is, the lighter the color) of a feature, the lower the strength of its predominant attribute compared to the total. In the per capita personal income example, this means that counties in which the predominant year is 2007 are drawn in different shades of blue to reflect the value of per capita personal income in 2007 as a percentage of the total per capita income value for all of the years.
To style features by predominant category, do the following:
- Follow the first five steps of Apply a style.
- Repeat the previous step to select up to nine more numeric attributes.
Each attribute should represent a distinct category related to the first attribute and should have the same unit of measure.
- Choose the Predominant category style and click Style options.
- Optionally, do the following:
- Click the color ramp under Symbol style and change the settings to choose a different color ramp or to change other graphic parameters, such as line width and outline pattern. For more information, see Use style options.
- Click the colored symbol next to the category in the list to customize the color of any of the categories individually. Available options depend on whether the data consists of points, lines, or polygons. For example, if the data consists of points, you can change the shape, fill color, stroke, and size of the point symbol.
- Click a label, type a new category label, and press Enter.
- Drag a category up or down in the list.
- If you are mapping point symbols, you can rotate symbols based on a second numeric attribute. For example, the color of the points depicts air temperature at weather stations, while the rotation of the points depicts humidity. The default symbol is round, which doesn't depict rotation well. It is best to choose a different shape. To rotate symbols, click Rotation by attribute and specify the rotation settings.
- Click Transparency by predominant percentage to adjust the transparency per feature based on the relative strength of the predominant attribute, ensure that the Set transparency based on the predominant percentage toggle button is turned on, and specify the transparency settings. Values reflect the relative strength of the predominant attribute as a percentage of the total value of all attributes. Features with a predominant percentage value above the upper handle value (high values) are drawn with the same transparency (darker or less transparent). Features with a predominant percentage value below the lower handle value (low values) are displayed with the same transparency (lighter or more transparent). The remaining features are drawn with continuous transparency between the two bounds. Experiment with the position of the handles and use the calculated average option to apply transparency effectively.
- Click Done when you are finished customizing the style, or click Cancel to return to the Styles pane without saving your choices.
Predominant category and Size
Use this map style to compare multiple related attributes with the same unit of measure. As with the Predominant category style, this style uses color to show the predominant attribute and uses transparency to show the degree of its predominance compared to the other attributes. In addition, the Predominant category and Size style uses a third element—size—to represent the sum of the attributes for each feature. For example, in a layer that shows types of housing by census tract, you can apply this style to see which housing type—owner occupied, renter occupied, or vacant—has the highest count in each census tract, and how much higher the predominant housing type's count is compared to the other types. In addition, by applying proportional symbols to the layer, you can compare the total number of housing units across tracts, visualizing tracts with high numbers of housing units and those with lower numbers.
To use the Predominant category and Size style, choose 2 to 10 numeric attributes with the same unit of measure (for example, units), each representing a distinct category (for example, owner occupied, renter occupied, or vacant) related to the subject of your map (for example, housing type). Each attribute is drawn with a different color, defined by the color ramp applied to the layer or by colors you apply to the individual attribute categories. As with the Predominant category style, this style uses transparency to show the relative strength of the predominant attribute (for example, renter-occupied units) compared to the total. Generally, higher transparency equates to lower strength (that is, a lower percentage of the total value of all attributes). For the size component of this style, proportional symbols are used to show the sum of the categories (for example, total housing units by census tract); larger symbols represent larger numbers.
To style features by predominant category and size, do the following:
- Follow the first five steps of Apply a style.
- Repeat the previous step to select up to nine more numeric attributes.
Each attribute should represent a distinct category related to the first attribute and should have the same unit of measure.
- Choose the Predominant category and Size style and click Style options.
- Define settings for Predominant category (attribute with the highest value) and Counts and Amounts (size) (sum of the categories).
- Click Done when you are finished customizing the style, or click Cancel to return to the Styles pane without saving your choices.
Relationship
Using the Relationship smart mapping style, you can visualize the relationship between two numeric attributes in point, line, or polygon feature data. For example, you can see whether there is a relationship between the richness and rarity of species in the world and in which areas the relationship is most pronounced. Based on the bivariate choropleth mapping technique, the Relationship style applies a distinct graduated color ramp to the classified data in each attribute and combines the color ramps, allowing you to see where the attributes may be related. You can explore the relationship using different focus options—for example, you can focus on where both richness and rarity of species are high, or change the focus to highlight areas where they are both low. You can also change the classification method and other settings.
To style features by relationship, do the following:
- Follow the first five steps of Apply a style.
- Repeat the previous step to select a second numeric attribute or Arcade expression.
- Choose the Relationship style and click Style options.
- Optionally, choose a different color ramp or change other graphic parameters, such as line width and outline pattern. Click the color ramp under Symbol style and change the settings. For more information, see Use style options.
- From the Grid size drop-down menu, choose the grid size to use for the legend.
The higher the grid numbers, the more detailed the color gradient in the color ramp is applied.
- From the Method drop-down menu, choose the classification method to classify the attribute values in the data. You can also click Legend to manually edit the symbols and labels for the classes in the map legend.
- For each attribute you're mapping, expand the attribute and choose an option from the Divided by drop-down menu. To change how the data is distributed, adjust the bounding handles along the histogram by either dragging the handle or clicking the number next to the handle and typing a value. You can also use calculated average to understand the distribution of the data and fine-tune the message of the map.
If the data isn’t normalized or standardized, you can turn the raw data into rates or percentages. Normalizing data is recommended when you're mapping relationships. Examples of normalized data include x per capita, y per square kilometer, or a ratio of x to y. Raw counts, by comparison, are better visualized with colors after they are standardized.
- Optionally, draw locations with missing data on the map. Turn on the Draw features with no values toggle button and optionally specify a style and label to represent those values.
- From the Focus drop-down menu, choose one of the following options to specify the aspect of the relationship to highlight:
- High values—The legend focuses on features with high values for both attributes.
- High values/Low values—The legend focuses on features with high values in the first attribute and low values in the second attribute.
- Low values/High values—The legend focuses on features with low values in the first attribute and high values in the second attribute.
- Low values—The legend focuses on features with low values for both attributes.
- None—The legend has no specific focus.
- Optionally, adjust the transparency of numeric values per feature. Click Transparency by attribute, turn on the Set transparency based on attribute values toggle button, and specify the transparency settings.
You can only use this option if you have numeric or date data associated with the locations. For example, if a layer contains population data, you can adjust the transparency of each location proportionally to its population.
- Optionally, if you're mapping point symbols, click Rotation by attribute and specify the rotation settings to
rotate symbols
based on a second numeric field.
For example, the color of the points depicts air temperature at weather stations, while the rotation of the points depicts humidity. The default symbol is round, which doesn't depict rotation well. It's best to choose a different shape.
- Click Done when you are finished customizing the style, or click Cancel to return to the Styles pane without saving your choices.
Relationship and Size
Use the Relationship and Size map style to see the relationship between numeric attributes in point, line, or polygon feature data. As with the Relationship style, this style applies distinct graduated color ramps to the classified data in two attributes and combines the color ramps to show relationships between the attributes. In addition, the Relationship and Size style uses different-sized symbols to represent a third numeric attribute you specify. For example, you can see whether there is a relationship between federal payments for conservation and wetland programs per operation and payments for farming programs per operation, and whether the total federal program payment amounts are consistent with the pattern. Using this map style, you can also visually identify the areas of the country where the relationship is most and least pronounced. The Relationship and Size style allows you to explore relationships in te data using focus options, classification methods, and other options.
- Follow the first five steps of Apply a style.
The first attribute is styled using color to show its potential relationship with the second attribute.
- Repeat the previous step to select a second and third numeric attribute or Arcade expression.
The second attribute is styled using color to show its potential relationship with the first attribute. The third attribute is styled on the map using different-sized symbols.
- Choose the Relationship and Size style and click Style options.
- Define settings for Relationship for the first two attributes and Counts and Amounts (size) for the third attribute.
- Optionally, adjust the transparency of numeric values per feature. Click Transparency by attribute, turn on the Set transparency based on attribute values toggle button, and specify the transparency settings.
- Optionally, if you're mapping point symbols, click Rotation by attribute and specify the rotation settings to
rotate symbols
based on a second numeric field.
For example, the color of the points depicts air temperature at weather stations, while the rotation of the points depicts humidity. The default symbol is round, which doesn't depict rotation well. It's best to choose a different shape.
- Click Done when you are finished customizing the style, or click Cancel to return to the Styles pane without saving your choices.