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Histogram

In this topic

  1. Summary
  2. Discussion
  3. Syntax
  4. Properties
  5. Method Overview
  6. Methods
  7. Code sample

Summary

The Histogram class creates histograms. 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 AllSource

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 Samples section for an example of how to specify arguments using keywords.

Syntax

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

The field name for the x-axis variable. The field must be a numeric field.

String
splitCategory

A categorical field that adds a separate series for each unique value in the field.

String
miniChartsPerRow

The number of minicharts that will be shown per row. The number of rows will be determined by the total number of series divided by the miniChartsPerRow value.

Integer
showPreviewChart

Specifies whether the preview chart will be displayed for grid charts.

  • True—The preview chart will be displayed.
  • False—The preview chart will not be displayed.

(The default value is False)

Boolean
binCount

The number of bins to display in the histogram.

Integer
showMean

Specifies whether the mean statistical line is visible in the histogram.

  • True—The mean line is visible in the histogram.
  • False—The mean line is not visible in the histogram.
Boolean
showMedian

Specifies whether the median statistical line is visible in the histogram.

  • True—The median line is visible in the histogram.
  • False—The median line is not visible in the histogram.
Boolean
showStandardDeviation

Specifies whether the standard deviation lines are visible in the histogram.

  • True—The standard deviation lines are visible in the histogram.
  • False—The standard deviation lines are not visible in the histogram.
Boolean
showComparisonDistribution

Specifies whether the normal distribution comparison line is visible in the histogram.

  • True—The comparison line is visible in the histogram.
  • False—The comparison line is not visible in the histogram.
Boolean
dataTransformationType

Specifies the data transformation type.

  • none—No transformation is applied.
  • logarithmic—A logarithmic transformation is applied.
  • squareRoot—A square root transformation is applied.
  • inverse—An inverse transformation is applied.
  • boxCox—A box-cox transformation is applied.
String
dataTransformationParameters

The data transformation parameters for the Box-Cox transformation. This parameter accepts a two-item list in which the first item is the power parameter and the second item is the shift parameter.

List
title

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

The description of the chart. The description text appears at the bottom of the chart view.

String
xTitle

The title of the x-axis of the chart.

String
yTitle

The title of the y-axis of the chart.

String
dataSource

The data source of the chart. When a chart is exported using the exportToSVG method or displayed in an ArcGIS Notebook, the data source will be read and rendered on the chart. Valid data sources include the following:

  • Paths to datasets, including local datasets, UNC paths, and service URLs
  • Arrow table objects
  • Layer or Table objects

Object
displaySize
[displaySize,...]

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 in which the first item is the width of the chart and the second item is the height of the chart.

List

Properties

PropertyExplanationData Type
binCount
(Read and Write)

The number of bins to display in the histogram.

Integer
dataSource
(Read and Write)

The data source of the chart. When a chart is exported using the exportToSVG method or displayed in an ArcGIS notebook, the data source will be read and rendered on the chart. Valid data sources include the following:

  • Paths to datasets, including local datasets, UNC paths, and service URLs
  • Arrow table objects
  • Layer or Table objects

Object
dataTransformationType
(Read and Write)

Specifies the data transformation type.

  • none—No transformation is applied.
  • logarithmic—A logarithmic transformation is applied.
  • squareRoot—A square root transformation is applied.
  • inverse—An inverse transformation is applied.
  • boxCox—A box-cox transformation is applied.
String
description
(Read and Write)

The description of the chart. The description text appears at the bottom of the chart view.

String
displaySize
(Read and Write)

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 in which the first item is the width of the chart and the second item is the height of the chart.

List
legend
(Read and Write)

The properties of the chart legend.

  • alignment—Specifies the alignment of the legend. Alignment options are left, bottom, top, and right.
  • title—The title of the legend.
  • visible—Specifies whether the legend will be displayed in the chart view. True displays the legend, and False hides the legend.
Object
miniChartsPerRow
(Read and Write)

The number of minicharts that will be shown per row. The number of rows will be determined by the total number of series divided by the miniChartsPerRow value.

Integer
showComparisonDistribution
(Read and Write)

Specifies whether the normal distribution comparison line is visible in the histogram.

  • True—The comparison line is visible in the histogram.
  • False—The comparison line not visible in the histogram.
Boolean
showMean
(Read and Write)

Specifies whether the mean statistical line is visible in the histogram.

  • True—The mean line is visible in the histogram.
  • False—The mean line is not visible in the histogram.
Boolean
showMedian
(Read and Write)

Specifies whether the median statistical line is visible in the histogram.

  • True—The median line is visible in the histogram.
  • False—The median line is not visible in the histogram.
Boolean
showPreviewChart
(Read and Write)

Specifies whether the preview chart will be displayed for grid charts.

  • True—The preview chart will be displayed.
  • False—The preview chart will not be displayed.
Boolean
showStandardDeviation
(Read and Write)

Specifies whether the standard deviation lines are visible in the histogram.

  • True—The standard deviation lines are visible in the histogram.
  • False—The standard deviation lines are not visible in the histogram.
Boolean
splitCategory
(Read and Write)

A categorical field that adds a separate series for each unique value in the field.

String
theme
(Read and Write)

The name of the theme that will be applied to the chart.

String
title
(Read and Write)

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 List By Drawing Order.

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;

  • addGuide—Adds a guide to the axis using a Guide object.
  • 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:

  • addGuide—Adds a guide to the axis using a Guide object.
  • 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

MethodExplanation
addToLayer (layer_or_layerfile)

The addToLayer method adds the chart object to a layer or table view.

exportToSVG (path, width, height)

The exportToSVG method exports the chart to SVG format.

updateChart ()

The updateChart method updates chart properties to sync changes between the object and the chart previously added to a layer.

Methods

addToLayer (layer_or_layerfile)
ParameterExplanationData Type
layer_or_layerfile

The chart will be added to the target object. This argument can be a Layer or Table object.

Object

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

Add a chart to an existing layer.

import arcpy

# Insert creation of chart object here
...

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)
ParameterExplanationData 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 AllSource. 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 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

# Insert creation of chart object here
...

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

# Set data source of chart object to a layer in 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.

import arcpy

# Insert creation of chart object here
...

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 ()

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

You can also modify the properties of the original chart instead of starting 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 allows 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.

import arcpy

# Insert creation of chart object here
...

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)

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In this topic
  1. Summary
  2. Discussion
  3. Syntax
  4. Properties
  5. Method Overview
  6. Methods
  7. Code sample