Drawing features to show quantities
Release 9.2 Last modified August 15, 2007	Print all topics in : "Applying symbology"

About representing quantative measures

In ArcMap, you can represent quantitative measures using color, symbol size, dot density, and charts.

Learn more about symbolizing data to represent quantity

How to symbolize quantitative data

Representing quantity with color

1. Right-click the layer you want to draw showing a quantitative value in the table of contents and click Properties.
   
2. Click the Symbology tab.
   
3. Click Quantities.
   
ArcMap automatically selects Graduated colors.

4. Click the Value drop-down arrow and click the field that contains the quantitative value you want to map.
   
5. Click the Normalization drop-down arrow and click a field to normalize the data.
   
ArcMap divides this field into the Value to create a ratio.

6. Click Classify.
   
7. Click the Method drop-down arrow and click the classification method you want to use.
   
8. Click the Classes drop-down arrow and click the number of classes you want to display.
   
9. Click OK on the Classification dialog box.
   
10. Click the Color Ramp drop-down arrow and click a ramp with which to display the data.
    
11. Click OK on the Layer Properties dialog box.
    

Tips

You can right-click a class to see additional options, such as sorting and number formatting. Use the graduated colors renderer to make choropleth maps. To learn about creating and working with color ramps, see Working with color ramps. The maximum sample size is maximum number of records to be considered for classifying data. Limiting the sample size protects you from reading potentially millions of records. If you want to change the maximum sample size, click the Sampling button on the Classification dialog box and type a new value.

Representing quantity with graduated symbols

1. Right-click the layer you want to draw showing a quantitative value in the table of contents and click Properties.
   
2. Click the Symbology tab.
   
3. Click Quantities and click Graduated symbols.
   
4. Click the Value drop-down arrow and click the field that contains the quantitative value you want to map.
   
5. Click the Normalization drop-down arrow and click a field to normalize the data.
   
ArcMap divides this field into the Value to create a ratio.

6. Type the minimum and maximum symbol sizes and click Classify.
   
7. Click the Method drop-down arrow and click the classification method you want to use.
   
8. Click the Classes drop-down arrow and click the number of classes you want to display.
   
Optionally, click Exclusion to remove unwanted values from the classification, for example, null values or extreme outliers.

9. Click OK on the Classification dialog box.
   
10. Click OK on the Layer Properties dialog box.
    

Tips

You can set the number format properties for the class range labels that appear in the legend and table of contents by clicking the Label column heading and clicking Format Labels. If you want your graduated symbols to get larger when you zoom in, set a reference scale. Right-click the data frame and click Set Reference Scale. Your symbols will appear at the same size on-screen as they are when your map is printed. You can set the number of significant digits for labels by clicking the Label column heading. This reveals a menu that lets you format the labels. All the symbols should be the same color. Make sure they're dark enough to be seen easily. If you are drawing them inside areas, use a light color to shade the areas. Click the Template button to choose another marker. If you click Background, you can choose the fill symbol that will be used behind your graduated symbols. The maximum sample size is maximum number of records to be considered for classifying data. Limiting the sample size protects you from reading potentially millions of records. If you want to change the maximum sample size, click the Sampling button on the Classification dialog box and type a new value. To change the color of a base symbol, see "Defining the color of a base symbol" in Working with color.

Representing quantity with proportional symbols

1. Right-click the layer you want to draw showing a quantitative value in the table of contents and click Properties.
   
2. Click the Symbology tab.
   
3. Click Quantities and click Proportional symbols.
   
4. Click the Value drop-down arrow and click the field that contains the quantitative value you want to map.
   
5. Click the Normalization drop-down arrow and click a field to normalize the data.
   
ArcMap divides this field into the Value to create a ratio.
Optionally, click Background and Min Value to change the symbol properties and background of the proportional symbols.

6. Click OK.
   

Tips

Proportional symbols cannot be converted to representation symbology because proportional symbols are not generated from a fixed symbol set. However, converting the layer's features into graphics is an option for gaining additional edit control with proportional symbols. Checking Appearance Compensation in the Symbol box turns on Flannery compensation, a technique that adjusts symbol sizes upward to account for the fact that map readers tend to underestimate the size of circular symbols. Click the Min Value button to choose another marker for your proportional symbols. If you click Background, you can choose the fill symbol that will be used behind your proportional symbols. If the symbol for the maximum value fills the space on the dialog box, it will probably be too large on the map. Try reducing the symbol size for the minimum value, normalizing the data, or excluding some values. If it's still too large, use graduated symbols instead. All the symbols should be the same color. Make sure they're dark enough to be seen easily. If you're drawing them inside areas, use a light color to shade the areas.

Representing quantity with proportional symbols when values are measurements

1. Right-click the layer you want to draw showing a quantitative value in the table of contents and click Properties.
   
2. Click the Symbology tab.
   
3. Click Quantities and click Proportional symbols.
   
4. Click the Value drop-down arrow and click the field that contains the quantitative value you want to map.
   
5. Click the Normalization drop-down arrow and click a field to normalize the data.
   
ArcMap divides this field into the Value to create a ratio.

6. Click the Unit drop-down arrow and click a unit.
   
7. Click Square or Circle as the symbol.
   
Optionally, change the color of the symbol and click Background to change the background of the proportional symbols.

8. Click Radius or Area.
   
9. Click OK.
   

Tips

Proportional symbols cannot be converted to representation symbology because proportional symbols are not generated from a fixed symbol set. However, converting the layer's features into graphics is an option for gaining additional edit control with proportional symbols. Checking Appearance Compensation in the Symbol box turns on Flannery compensation, a technique that adjusts symbol sizes upward to account for the fact that map readers tend to underestimate the size of circular symbols. Click the Min Value button to choose another marker for your proportional symbols. If you click Background, you can choose the fill symbol that will be used behind your proportional symbols. If the symbol for the maximum value fills the space on the dialog box, it will probably be too large on the map. Try reducing the symbol size for the minimum value, normalizing the data, or excluding some values. If it's still too large, use graduated symbols instead. All the symbols should be the same color. Make sure they're dark enough to be seen easily. If you're drawing them inside areas, use a light color to shade the areas.

Representing quantity with a dot density map

1. Right-click the layer you want to draw showing a quantitative value using dot densities in the table of contents and click Properties.
   
2. Click the Symbology tab.
   
3. Click Quantities and click Dot density.
   
4. Click the field or fields under Field Selection that contain the quantitative values that you want to map.
   
5. Click the arrow button to add fields to the field list.
   
6. Double-click a dot symbol in the field list to change its properties.
   
7. Type the dot size or click the slider to adjust the size.
   
8. Type the dot value or click the slider to adjust the value.
   
9. Check Maintain Density to preserve the dot density.
   
When checked, as you zoom in, the dot size will increase so a given area will visually appear as dense. Otherwise, the dot size will remain constant.
Optionally, click Properties to set the dot placement options and use masking.

10. Click OK.
    

Tips

When creating a dot density map, you specify how many features each dot represents and the size of the dots. You may need to try several combinations of amount and size to see which one best shows the pattern. In general, you should choose values that ensure the dots are not so close as to form solid areas that obscure the patterns or so far apart as to make the variations in density hard to see. In most cases, you'll only map one field using a dot density map. In special cases, you may want to compare distributions of different types and may choose to map two or three fields. You can click the Exclusion button to type or load an SQL expression to exclude any values you don't want mapped. You have two options for placing your dots within an area: Non-fixed Placement, the default option, indicates that the dots will be placed randomly each time the map is refreshed, while Fixed Placement freezes the placement of dots, even if the map is refreshed.

Drawing bar and column charts

1. Right-click the layer you want to draw showing quantitative values with bar or column charts in the table of contents and click Properties.
   
2. Click the Symbology tab.
   
3. Click Charts and click Bar/Column.
   
4. Click one or more fields under Field Selection that contain the quantitative values you want to map.
   
5. Click the arrow button to add fields to the field list.
   
6. Click the Color Scheme drop-down arrow and click the colors you want to use.
   
You can double-click an individual symbol in the list to change its properties.

7. Check the box to prevent the charts from overlapping.
   
8. Click Size.
   
9. Type a maximum length or click the arrows to set the length and click OK.
   
10. Click OK.
    

Tips

You can click the Exclusion button to type or load an SQL expression to exclude any values you don't want charted. Since the charts represent categories, not relative amounts, draw the bars or wedges using different colors, rather than shades of one color. Charts are most effective when mapping no more than 30 features. Otherwise, the patterns on the map will be difficult to see. In addition, don't use more than five categories on a chart; if you want to show more categories, a series of shaded maps showing each category will work better.

Drawing stacked charts

1. Right-click the layer you want to draw showing quantitative values with stacked charts in the table of contents and click Properties.
   
2. Click the Symbology tab.
   
3. Click Charts and click Stacked.
   
4. Click the fields under Field Selection that contain the quantitative values you want to map.
   
Choosing more than one field shows the relationship to the whole.

5. Click the arrow button to add fields to the field list.
   
6. Click the Color Scheme drop-down arrow and click the colors you want to use.
   
You can double-click an individual symbol in the list to change its properties.

7. Check the box to prevent the charts from overlapping.
   
8. Click Size.
   
9. Type a maximum length or click the arrows to set the length and click OK.
   
10. Click OK.
    

Tips

Avoid using stacked charts with data containing negative values. You can click the Exclusion button to type or load an SQL expression to exclude any values you don't want charted. Since the charts represent categories, not relative amounts, draw the bars or wedges using different colors rather than shades of one color. Charts are most effective when mapping no more than 30 features. Otherwise, the patterns on the map will be difficult to see. In addition, don't use more than five categories on a chart; if you want to show more categories, a series of shaded maps showing each category will work better.

Drawing pie charts

1. Right-click the layer you want to draw showing quantitative values with charts in the table of contents and click Properties.
   
2. Click the Symbology tab.
   
3. Click Charts and click Pie.
   
4. Click the fields under Field Selection that contain the quantitative values you want to map.
   
Choosing more than one field shows the relationship to the whole.

5. Click the arrow button to add fields to the field list.
   
6. Click the Color Scheme drop-down arrow and click the colors you want to use or double-click a symbol in the list to change its properties.
   
7. Check the box to prevent the charts from overlapping.
   
8. Click Size.
   
9. Click the Variation Type you want to use.
   
You can either draw all pies the same size or vary the size based on the sum of the attributes or a particular attribute value.

10. Type a size or click the arrows to set the size and click OK.
    
11. Click OK.
    

Tips

Avoid using pie or stacked bar charts with data containing negative values. Checking Appearance Compensation on the Pie Chart Size dialog box turns on Flannery compensation, a technique that adjusts symbol sizes upward to account for the fact that map readers tend to underestimate the size of circular symbols. You can click the Exclusion button to type or load an SQL expression to exclude any values you don't want charted. Since the charts represent categories, not relative amounts, draw the bars or wedges using different colors rather than shades of one color. Charts are most effective when mapping no more than 30 features. Otherwise, the patterns on the map will be difficult to see. In addition, don't use more than five categories on a chart; if you want to show more categories, a series of shaded maps showing each category will work better.

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