Create heatmap chart
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Syntax
heatmap(tbl,xvar,yvar)
heatmap(tbl,xvar,yvar,'ColorVariable',cvar)
heatmap(cdata)
heatmap(xvalues,yvalues,cdata)
Description
Table Data
example
heatmap(tbl,xvar,yvar)
creates a heatmap by aggregating the variables in the table tbl
. Specify xvar
and yvar
as the table variables that you want to visualize. The numbers in the cells and the default colors correspond to the number of times each (x, y) pair appears together in the table. The resulting x-axis and y-axis show unique values from the xvar
and yvar
variables respectively.
example
heatmap(tbl,xvar,yvar,'ColorVariable',cvar)
uses the table variable specified by cvar
to calculate the numbers in the cells and the corresponding colors. The default calculation method is a mean aggregation, so the cell numbers and colors are based on the average value of cvar
for each (x, y) pair that appears together in the table.
Matrix Data
example
heatmap(cdata)
creates a heatmap from the 2-D matrix cdata
, which contains pre-aggregated data. The heatmap has one cell for each value in cdata
.
example
heatmap(xvalues,yvalues,cdata)
specifies the labels for the values that appear along the x-axis and y-axis.
Additional Options
example
heatmap(___,Name,Value)
specifies additional options for the heatmap using one or more name-value pair arguments. Specify the options after all other input arguments. For a list of properties, see HeatmapChart Properties.
heatmap(parent,___)
creates the heatmap in the figure, panel, or tab specified by parent
.
h = heatmap(___)
returns the HeatmapChart
object. Use h
to modify properties of the chart after creating it. For a list of properties, see HeatmapChart Properties.
Examples
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Create Heatmap from Tabular Data
Open Live Script
Create a heatmap from a table of data for medical patients.
Load the patients
data set and create a table from a subset of the variables loaded into the workspace. Then create a heatmap that counts the total number of patients with the same set of Smoker
and SelfAssessedHealthStatus
values.
load patientstbl = table(LastName,Age,Gender,SelfAssessedHealthStatus,... Smoker,Weight,Location);h = heatmap(tbl,'Smoker','SelfAssessedHealthStatus');
Reorder Heatmap Labels
Open Live Script
Create a heatmap and reorder the labels along the y-axis.
Load the patients
data set and create a heatmap from the data. Assign the HeatmapChart
object to the variable h
.
load patientstbl = table(LastName,Age,Gender,SelfAssessedHealthStatus,... Smoker,Weight,Location);h = heatmap(tbl,'Smoker','SelfAssessedHealthStatus');
Reorder the labels along the y-axis.
h.YDisplayData = {'Excellent','Good','Fair','Poor'};
Alternatively, you can reorder the labels by changing the data to categorical data and then reordering the categories using the reordercats function. Similarly, you can add, remove, or rename the heatmap labels using the addcats, removecats, or renamecats functions, respectively.
Specify Table Variable for Heatmap Colors
Open Live Script
Create a heatmap and specify the table variable to use when determining the heatmap cell colors.
Load the patients
data set and create a heatmap from the data. Color each cell using the average age of patients with a particular pair of Smoker
and SelfAssessedHealthStatus
values by setting the ColorVariable
option to 'Age'
.
load patientstbl = table(LastName,Age,Gender,SelfAssessedHealthStatus,... Smoker,Weight,Location);h = heatmap(tbl,'Smoker','SelfAssessedHealthStatus',... 'ColorVariable','Age');
Specify Calculation Method for Color Data
Open Live Script
Create a heatmap and specify the table variable and calculation method to use when determining the heatmap cell colors.
Load the patients data set and create a heatmap from the data. Color each cell using the median age of patients with a particular pair of Smoker
and SelfAssessedHealthStatus
values. Specify the ColorVariable
option as 'Age'
and the ColorMethod
option as 'median'
.
load patientstbl = table(LastName,Age,Gender,SelfAssessedHealthStatus,... Smoker,Weight,Location);h = heatmap(tbl,'Smoker','SelfAssessedHealthStatus',... 'ColorVariable','Age','ColorMethod','median');
Create Heatmap from Matrix Data
Open Live Script
Create a matrix of data. Then create a heatmap of the matrix values. The default labels along the x-axis and y-axis appear as 1, 2, 3, and so on.
cdata = [45 60 32; 43 54 76; 32 94 68; 23 95 58];h = heatmap(cdata);
Create Heatmap from Matrix Data Using Custom Axis Labels
Open Live Script
Create a matrix of data. Then create a heatmap of the matrix values. Use custom labels along the x-axis and y-axis by specifying the first two input arguments as the labels you want. Specify the title and axis labels by setting properties of the HeatmapChart
object.
cdata = [45 60 32; 43 54 76; 32 94 68; 23 95 58];xvalues = {'Small','Medium','Large'};yvalues = {'Green','Red','Blue','Gray'};h = heatmap(xvalues,yvalues,cdata);h.Title = 'T-Shirt Orders';h.XLabel = 'Sizes';h.YLabel = 'Colors';
Use LaTeX for Greek Letters in Title
Since R2023b
Open Live Script
To use LaTeX (or TeX) markup in the title, axis labels, or data tips, set the Interpreter
property of the HeatmapChart
object.
For example, create a heatmap chart with a title that uses LaTeX to display Greek letters. Set the Interpreter
property to "latex"
when you create the chart. Then include the markup when you call the title
function.
heatmap(randi(100,5,3),Interpreter="latex")title("$\hat{\psi_1}$ Values for ${1\le\alpha\le3}$")
Normalize Colors Along Each Row or Column
Open Live Script
Create a heatmap and normalize the colors along each column or row by setting the ColorScaling
property.
Read the sample file outages.csv
into a table. The sample file contains data representing electric utility outages in the Unites States. The table contains six columns: Region
, OutageTime
, Loss
, Customers
, RestorationTime
, and Cause
. Display the first five rows of each column.
T = readtable('outages.csv');T(1:5,:)
ans=5×6 table Region OutageTime Loss Customers RestorationTime Cause _____________ ________________ ______ __________ ________________ ___________________ {'SouthWest'} 2002-02-01 12:18 458.98 1.8202e+06 2002-02-07 16:50 {'winter storm' } {'SouthEast'} 2003-01-23 00:49 530.14 2.1204e+05 NaT {'winter storm' } {'SouthEast'} 2003-02-07 21:15 289.4 1.4294e+05 2003-02-17 08:14 {'winter storm' } {'West' } 2004-04-06 05:44 434.81 3.4037e+05 2004-04-06 06:10 {'equipment fault'} {'MidWest' } 2002-03-16 06:18 186.44 2.1275e+05 2002-03-18 23:23 {'severe storm' }
Create a heatmap that shows the different regions along the x-axis and the different outage causes along the y-axis. In each cell, show how many times each region experienced a power outage due to a particular cause.
h = heatmap(T,'Region','Cause');
Normalize the colors along each column. The smallest value in each column maps to the first color in the colormap and the largest value maps to the last color. The last color indicates the cause that caused the most power outages for each region.
h.ColorScaling = 'scaledcolumns';
Normalize the colors along each row instead. The smallest value in each row maps to the first color in the colormap and the largest value maps to the last color. The last color indicates the region that experienced the most power outages due to each cause.
h.ColorScaling = 'scaledrows';
Compute Color Data Using Custom Aggregation Method
Open Live Script
Create a heatmap and color the cells using data computed with a custom aggregation method. Use the pivot
function to compute the color data.
Read the sample file TemperatureData.csv
into a table. The file contains four columns: Year
, Month
, Day
, and TemperatureF
.
tbl = readtable('TemperatureData.csv');
Compute the color data as the maximum temperature for each month and year combination using the pivot
function. Use NaN
for missing month and year combinations.
P = pivot(tbl,Columns="Month",Rows="Year",DataVariable="TemperatureF",Method=@(x) mean(x,"includenan"))
P=2×13 table Year April August December February January July June March May November October September ____ ______ ______ ________ ________ _______ ______ ______ ______ ______ ________ _______ _________ 2015 43.267 69.903 40.548 15.448 21.355 69.161 59.967 28.484 57.548 43.8 49.323 64.467 2016 42.267 NaN NaN 29.966 27.71 68.824 63.733 37.806 53.806 NaN NaN NaN
Rearrange the variables in the pivoted table.
P = P(:,["Year" "January" "February" "March" "April" "May" "June" "July" "August" "September" "October" "November" "December"]);
Create the heatmap, and color the heatmap cells using the computed data values.
xvar = P.Properties.VariableNames(2:end);yvar = string(P.(1));cvar = P{:,2:end};heatmap(xvar,yvar,cvar)title("Maximum Temperatures (F)")
Compare Heatmaps with Different Numbers of Colors
Open Live Script
Heatmap charts use the 256-sampling of the sky
colormap by default. You can change the sampling by specifying the Colormap
name-value argument.
For example, create two heatmap charts in a 2-by-1 tiled chart layout. The top chart uses the default set of 256 colors, and the bottom chart uses only two colors.
tiledlayout(2,1,TileSpacing="compact")% Top chart with default colorsnexttileheatmap(magic(10))% Bottom chart with two colorsnexttileheatmap(magic(10),Colormap=sky(2))
Input Arguments
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tbl
— Source table
table | timetable
Source table, specified as a table or timetable.
You can create a table from workspace variables using the table function, or you can import data as a table using the readtable function. You can create a timetable from workspace variables using the timetable function.
The SourceTable property of the HeatmapChart
object stores the source table.
xvar
— Table variable for x-axis
character vector | string scalar | numeric scalar | logical vector
Table variable for x-axis, specified in oneof these forms:
Character vector or string scalar indicating one of the variable names. For example,
heatmap(tbl,'HealthStatus','Gender')
selects the variable named'HealthStatus'
for the x-axis.Numeric scalar indicating the table variable index.For example,
heatmap(tbl,2,3)
selects the secondvariable in the table for the x-axis.Logical vector containing one
true
element.
The values associated with your table variable must be groupedinto a finite set of discrete categories that the categorical function accepts. If thevalues are not grouped into a finite set of categories, use the discretize function to group them.
The labels that appear along the x-axisare in alphabetical order. You can customize the labels using categoricalarrays. For an example, see Create Heatmap from Tabular Data.
The XVariable property of the HeatmapChart
objectstores the selected variable.
yvar
— Table variable for y-axis
character vector | string scalar | numeric scalar | logical vector
Table variable for y-axis, specified in oneof these forms:
Character vector or string scalar of one of the variable names. For example,
heatmap(tbl,'HealthStatus','Gender')
selects the variable named'Gender'
for the y-axis.Numeric scalar indicating the table variable index.For example,
heatmap(tbl,2,3)
selects the thirdvariable in the table for the y-axis.Logical vector containing one
true
element.
The values associated with your table variable must be groupedinto a finite set of discrete categories that the categorical function accepts. If thevalues are not grouped into a finite set of categories, use the discretize function to group them.
The labels that appear along the y-axisare in alphabetical order. You can customize the labels using categoricalarrays. For an example, see Create Heatmap from Tabular Data.
The YVariable property of the HeatmapChart
objectstores the selected variable.
cvar
— Table variable for color data
character vector | string scalar | numeric scalar | logical vector
Table variable for color data, specified in one of these forms:
A character vector or string scalar of one of the variable names. For example,
heatmap(__,'ColorVariable','HealthStatus')
selects the variable named'HealthStatus'
for the y-axis.A numeric scalar indicating the table variable index.For example,
heatmap(__,'ColorVariable',1)
selectsthe third variable in the table for the y-axis.A logical vector containing one
true
element.
The values associated with your table variable must be of anumeric type or logical
.
The property value is empty []
when using matrix data. The ColorVariable
property of the HeatmapChart
object stores the selected variable. The ColorData
property populates with data based on the selected variable.
By default, heatmap
calculates the colordata based on a mean aggregation. To change the calculation method,set the ColorMethod property.
cdata
— Color data
matrix
Color data for the heatmap cells, specified as a matrix.
The ColorData
property of the HeatmapChart
object stores the values.
Example: [40 24 68; 68 37 58; 49 23 46]
xvalues
— Values appearing along x-axis
categorical array | string array | numeric array | cell array of character vectors
Values appearing along the x-axis, specifiedas a categorical array, string array, numeric array, or cell arrayof character vectors.
Example: {'small','medium','large'}
Example: categorical({'small','medium','large'})
yvalues
— Values appearing along y-axis
categorical array | string array | numeric array | cell array of character vectors
Values appearing along y-axis, specifiedas a categorical array, string array, numeric array, or cell arrayof character vectors.
Example: {'small','medium','large'}
Example: categorical({'small','medium','large'})
parent
— Parent container
Figure
object | Panel
object | Tab
object | TiledChartLayout
object | GridLayout
object
Parent container, specified as a Figure
, Panel
, Tab
, TiledChartLayout
, or GridLayout
object.
Name-Value Arguments
Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN
, where Name
is the argument name and Value
is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.
Before R2021a, use commas to separate each name and value, and enclose Name
in quotes.
Example: heatmap(tbl,xvar,yvar,'ColorVariable','Temperatures','ColorMethod','median')
Note
The properties listed here are only a subset. For a completelist, see HeatmapChart Properties.
Output Arguments
collapse all
h
— Heatmap chart object
HeatmapChart
object
HeatmapChart
object, which is a standalone visualization. Use h
to set properties on the heatmap chart after creating it.
More About
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Standalone Visualization
A standalone visualization is a chart designed for a special purpose that works independently from other charts. Unlike other charts such as plot
and surf
, a standalone visualization has a preconfigured axes object built into it, and some customizations are not available. A standalone visualization also has these characteristics:
It cannot be combined with other graphics elements, such as lines, patches, or surfaces. Thus, the
hold
command is not supported.The
gca
function can return the chart object as the current axes.You can pass the chart object to many MATLAB functions that accept an axes object as an input argument. For example, you can pass the chart object to the
title
function.
Tips
To interactively explore the data in your heatmap, use these options.
Zoom — Use the scroll wheel or the + and - keys to zoom.
Pan — Click and drag the heatmap or use the arrow keys to pan across the rows or columns.
Data tips — Hover over the heatmap to display a data tip.
Rearrange rows and columns — Click and drag a row or column label to move it to a different position.
Sort values — Click the icon that appears when you hover over the row or column label. Click once to sort the values in ascending order, twice to sort the values in descending order, and a third time to reset the order.
If you create a heatmap chart from a table, then you can customize its data tips.
To add or remove a row from the data tip, right-click anywhere on the chart and point to Modify Data Tips. Then, select or deselect a variable.
To add or remove multiple rows, right-click on the chart, point to Modify Data Tips, and select More. Then, add variables by clicking >> or remove them by clicking <<.
Version History
Introduced in R2017a
expand all
R2019a: Heatmaps interpret text using TeX markup
Starting in R2019a, heatmaps interpret text using TeX markup instead of displaying the literal characters. If you want to use a TeX markup character in regular text, such as an underscore (_), then insert a backslash (\) before the character you want to include. The backslash is the TeX escape character. For more information on using TeX markup, see the Interpreter property of the text object.
See Also
Functions
- sorty | sortx | pivot | table | readtable | categorical | sky
Properties
- HeatmapChart Properties
Topics
- Create Heatmap from Tabular Data
- Access Data in Tables
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