Histogram

Summary

Histograms visually summarize the distribution of a continuous numeric variable by measuring the frequency at which certain values appear in the dataset.

Learn more about histograms in ArcGIS Pro

Discussion

When creating a chart object, optional arguments for the class constructor must be specified using the argument name; they cannot be specified by argument position. See the code sample section for an example of how to specify arguments using keywords.

Syntax

Histogram (x, {binCount}, {showMean}, {showMedian}, {showStandardDeviation}, {showComparisonDistribution}, {dataTransformationType}, {dataTransformationParameters}, {title}, {description}, {xTitle}, {yTitle}, {dataSource}, {displaySize})

Parameter	Explanation	Data Type
x	The field name for the x-axis variable. The field must be a numeric field.	String
binCount	The number of bins to display in the histogram.	Integer
showMean	Indicates whether the mean statistical line is visible in the histogram. True displays the line. False hides the line.	Boolean
showMedian	Indicates whether the median statistical line is visible in the histogram. True displays the line. False hides the line.	Boolean
showStandardDeviation	Indicates whether the standard deviation statistical line is visible in the histogram. True displays the line. False hides the line.	Boolean
showComparisonDistribution	Indicates whether the normal distribution comparison line is visible in the histogram. True displays the line. False hides the line.	Boolean
dataTransformationType	The data transformation type. Supported transformations are none, logarithmic, squareRoot, inverse, and boxCox.	String
dataTransformationParameters	The data transformation parameters for the Box-Cox transformation. This parameter accepts a two-item list where the first item is the power parameter and the second item is the shift parameter.	List
title	Sets the title of the chart. The title text appears at the top of the chart view and is used as the label for the chart in the Contents pane.	String
description	Sets the description of the chart. The description text appears at the bottom of the chart view.	String
xTitle	Sets the title for the x-axis of the chart.	String
yTitle	Sets the title for the y-axis of the chart.	String
dataSource	Sets the data source of the chart. When a chart is exported using the exportToSVG method or displayed in an ArcGIS Notebook, the data source is read and rendered on the chart. Valid data sources include paths to datasets, including local datasets, UNC paths, and service URLs, and arcpy.mp Layer objects.	Object
displaySize [displaySize,...]	Sets the size of the chart when exported using the exportToSVG method or displayed in an ArcGIS Notebook. The value must be specified as a two-item list, where the first item is the width of the chart and the second item is the height of the chart.	List

Properties

Property	Explanation	Data Type
binCount (Read and Write)	The number of bins to display in the histogram.	Integer
dataSource (Read and Write)	Sets the data source of the chart. When a chart is exported using the exportToSVG method or displayed in an ArcGIS Notebook, the data source is read and rendered on the chart. Valid data sources include paths to datasets, including local datasets, UNC paths, and service URLs, and arcpy.mp Layer objects.	Object
dataTransformationType (Read and Write)	The data transformation type. Supported transformations are none, logarithmic, squareRoot, inverse, and boxCox	String
description (Read and Write)	Sets the description of the chart. The description text appears at the bottom of the chart view.	String
displaySize (Read and Write)	Sets the size of the chart when exported using the exportToSVG method or displayed in an ArcGIS Notebook. The value must be specified as a two-item list, where the first item is the width of the chart and the second item is the height of the chart.	List
legend (Read and Write)	Sets the properties of the chart legend. visible—Indicates whether the legend is visible in the chart view. True displays the legend. False hides the legend. title—The title to display for the legend.	Object
showComparisonDistribution (Read and Write)	Indicates whether the normal distribution comparison line is visible in the histogram. True displays the line. False hides the line.	Boolean
showMean (Read and Write)	Indicates whether the mean statistical line is visible in the histogram. True displays the line. False hides the line.	Boolean
showMedian (Read and Write)	Indicates whether the median statistical line is visible in the histogram. True displays the line. False hides the line.	Boolean
showStandardDeviation (Read and Write)	Indicates whether the standard deviation statistical line is visible in the histogram. True displays the line. False hides the line.	Boolean
title (Read and Write)	Sets the title of the chart. The title text appears at the top of the chart view and is used as the label in the Contents pane on the List By Drawing Order tab .	String
type (Read Only)	The string value indicating the chart type.	String
x (Read and Write)	The field name for the x-axis variable. The field must be a numeric field.	String
xAxis (Read and Write)	Sets the properties of the x-axis. field—The field name for the x-axis variable. The field must be a numeric field. logarithmic—This property is not supported for the Histogram class. maximum—The maximum axis bound. minimum—The minimum axis bound. sort—This property is not supported for the Histogram class. title—The label of the axis that displays on the chart.	Object
yAxis (Read and Write)	Sets the properties of the y-axis. field—This property is not supported for the Histogram class. logarithmic—This property is not supported for the Histogram class. maximum—The maximum axis bound. minimum—The minimum axis bound. sort—This property is not supported for the Histogram class. title—The label of the axis that displays on the chart.	Object

Method Overview

Method	Explanation
addToLayer (layer_or_layerfile)	Adds the chart object to a layer or stand-alone table.
exportToSVG (path, width, height)	Exports the chart to SVG format.
updateChart ()	Updates chart properties to sync changes between the object and the chart previously added to a layer.

Methods

addToLayer (layer_or_layerfile)

Parameter	Explanation	Data Type
layer_or_layerfile	The chart will be added to the target object. The layer_or_layerfile argument can be a Layer or a Table object.	Object

Often the final step after defining chart properties is to add the chart object to a layer or table using the addToLayer method.

Add a chart to an existing layer.

import arcpy

aprx = arcpy.mp.ArcGISProject("current")
map = aprx.listMaps()[0]
censusLayer = map.listLayers('Census Block Groups')[0]

# Add chart object to a layer
chart.addToLayer(censusLayer)

exportToSVG (path, width, height)

Parameter	Explanation	Data Type
path	The path where the chart will be exported in SVG format.	String
width	The width of the output graphic.	Integer
height	The height of the output graphic.	Integer

In some cases, you may want to save the chart as a graphic that can be shared and viewed outside of ArcGIS Pro. Exporting to the SVG graphic format is beneficial, as the chart elements and text are stored as vector elements that can be independently modified in a vector graphics software. An SVG graphic can also be resized to any scale without pixelation or loss in quality.

Export a chart that has a project layer data source to an .svg file.

import arcpy

aprx = arcpy.mp.ArcGISProject('current')
censusLayer = aprx.listMaps()[0].listLayers('Census Block Groups')[0]

# Set data source of chart object to a layer within current project
chart.dataSource = censusLayer

# Save the chart to file with dimensions width=500, height=500
chart.exportToSVG('populationByState.svg', 500, 500)

Export a chart that has a feature service data source to an .svg file.

featureServiceURL = r'https://services1.arcgis.com/hLJbHVT9ZrDIzK0I/arcgis/rest/services/CrimesChiTheft/FeatureServer/0'

# Set data source of chart object to a feature service URL
chart.dataSource = featureServiceURL

# Save the chart to file with dimensions width=800, height=600
chart.exportToSVG('theftsPerBeat.svg', 800, 600)

updateChart ()

Often the final step after defining chart properties is to add the chart object to a layer using the addToLayer method.

To further modify the chart properties, you can modify the properties of the original chart instead of starting from scratch with a new chart. You can then use the updateChart method to synchronize any changes into the chart that was added to the layer. This will allow the changes you make to be presented in the Chart properties pane and chart view.

Use the updateChart method to synchronize chart property changes into a layer.

chart.addToLayer(myLayer)

# Further modification is necessary
chart.description = "Data from the U.S. Census Bureau"
chart.updateChart()

Code sample

Create a histogram using a layer name as the data source and export the histogram to an .svg file.

import arcpy
chart = arcpy.charts.Histogram("price", binCount=20, showMedian=True)																											
chart.dataSource = "airbnb_listings"
chart.title = "Distribution of AirBnB Listing Price"
chart.exportToSVG("histogram.svg", width=1000, height=800)