Bar charts can be generated for any raster that has an attribute table. They can be used to summarize and compare categorical raster data by using proportional bar lengths to represent values.
Bar charts are composed of an x-axis and a y-axis. The x-axis represents discrete categories that correspond to one or many bars. Each bar’s height corresponds to a numeric value, which is measured by the y-axis.
Bar charts display unique category values from a Category or Date field as bars along the x-axis. The height of the bars corresponds to raw or aggregated numeric values.
If the values in the category variable are unique (only appear in the attribute field once), no aggregation is necessary, but a Numeric field must be specified. For example, if the category variable is VegetationType and the table only has one record for each type of vegetation, the bar heights will be determined by the Numeric field, and no aggregation is needed.
If the category values repeat in the table, an aggregation method must be chosen to specify how the data will be summarized.
If no Numeric fields are specified, the chart will use the count aggregation method, which totals the number of times each unique category appears in the category field. For example, the category variable is set to ClassName for a state land cover dataset with a count aggregation method. The resulting chart will display one bar for each land cover class, and the bar heights will represent the number of pixels in each class.
If Numeric field(s) are specified, the aggregation method can be one of the following:
More than one numeric field, or series, can be displayed for each discrete category value on the x-axis.
Multiple series bar charts can be created by adding multiple Numeric fields, or by setting a Split by category field.
When multiple Numeric fields are added, one bar will be drawn for each field at each category value on the x-axis. For example, the category variable is set to ClassName for a multidimensional land cover dataset with a Sum Aggregation method and two Numeric fields, Count2010 and Count2015. The resulting chart will display two bars for each land cover class. One bar will represent the sum of all pixels in each land cover class for 2010, and the second will represent the sum of all pixels for each land cover class for 2015. This will allow you to visualize how land cover has changed over time.
Each category in a bar chart can also be split into multiple series by another category field's values. A Split by category cannot be applied when more than one Numeric field has been added.
Category fields with many unique values are not appropriate for splitting a field into multiple series.
Display multiple series
When a bar chart contains multiple series, they will be displayed as Side-by-side bars by default. When the multiple series represent a part-to-whole relationship (in other words, all of the series combined add up to 100 percent of the category), they can also be represented using Stacked bars or 100% Stacked bars.
Side-by-side bars are best for comparing the individual values of each series across different categories. Stacked bars are best used when you are more interested in the totals for each category, but would like a sense of their series breakdown. 100% Stacked bars are used when you are only interested in visualizing the part-to-whole relationship without absolute totals.
Bar charts are composed of an x-axis and a y-axis. The x-axis represents discrete categories that correspond to one or many bars. The y-axis represents the raw or aggregated number of pixels in each category.
X-axis label character limit
Category labels are truncated at 11 characters by default. When labels are truncated, the full text is available by hovering. To display the entire label text in the chart, increase the label character limit.
Default y-axis bounds are set based on the range of data values represented on the y-axis. These values can be customized by typing a new desired axis bound value. Setting a y-axis bound can be used to keep the scale of your chart consistent for comparison. Clicking the reset button will revert the axis bound to the default value.
Since bar charts use length to represent relative value, it is important that all bar charts include an origin of zero.
You can format the way an axis displays numeric values by specifying a number format category or by defining a custom format string. For example, $#,### can be used as a custom format string to display currency values.
The design and format of your bar chart can edited by accessing the tabs in the Chart Properties pane.
Titles and description
Charts and axes are given default titles based on the variable names and chart type. These can be edited on the General tab in the Chart Properties pane. You can also provide a chart Description, which is a block of text that appears at the bottom of the chart window.
You can configure the look of your chart by formatting text and symbol elements, or by applying a chart theme. Format properties can be configured on the Format tab in the Chart Properties pane, or through the Chart Format context ribbon. Chart formatting options include the following:
- Size, color, and style of the font used for axis titles, axis labels, description text, legend title, legend text, and guide labels
- Color, width, and line type for grid and axis lines
- Background color of the chart
Colors can be changed on the Series tab in the Chart Properties pane by clicking the Symbol color patch in the Series table and choosing a new color.
Bar charts are automatically sorted alphabetically by their categories (x-axis ascending).
Labels displaying the value of each bar or series can be turned on by checking the Label bars check box on the Data tab in the Chart Properties pane.
Bars can be drawn horizontally by clicking the Rotate chart button in the chart window.
Guide lines or ranges can be added to charts as a reference or way to highlight significant values. To add a new guide, browse to the Guides tab in the Chart Properties pane and click Add guide. To draw a line, enter a Value where you would like the line to draw. To create a range, enter a to value. You can optionally add text to your guide by specifying a Label.
Create a bar chart to compare the distribution of pixels for different land cover types in a classified raster.
- Category or Date—ClassName
- Numeric field—Count