How to generate a heat map using imported data with (x,y, z as color)

Question

Prosopo 2019-11-16

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https://ww2.mathworks.cn/matlabcentral/answers/491466-how-to-generate-a-heat-map-using-imported-data-with-x-y-z-as-color

评论： Jyothis Gireesh 2019-11-22

I have imported a very large data file into MATLAB. I am curious how I can generate a heat map of the values using z as color so that the higher z values are more intense in color?

I have labled the imported file 'A' which is a 5798000x3 table. I have had success plotting the table using:

x = A{:,1};
y = A{:,2};
z = A{:,3};
figure(1)
plot3(Ax,Ay,Az)
grid on

however I would like to generate a heat map of the data.

Thanks in advance!

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Answer 1

Jyothis Gireesh 2019-11-19

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You may use the following syntax to create the heat map.

h = heatmap(tbl,xvar,yvar,'ColorVariable',cvar) 

where

“tbl” is the table name “A”
“xvar” indicates the variable name of the column to be displayed along the x-axis
“yvar” indicates the variable name of the column to be displayed along the y-axis
Specify “cvar” to control the heat map values according to the variable values. In this case, “cvar” corresponds to the 3rd column name.

Also, please refer to the following documentation link about creating heatmaps and customizing them

https://www.mathworks.com/help/matlab/ref/heatmap.html

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Prosopo 2019-11-21

在 MATLAB Online 中打开

I have incorporated the above mentioned syntax, however I have run across the error:

Warning: Error updating HeatmapChart.

Values in the source table variable 'Ay' are not grouped into discrete categories. Use the discretize function to group your values.

I am using the following:

Ax = A{:,1};
Ay = A{:,2};
Az = A{:,3};
A = table(Ax,Ay,Az);
h = heatmap(A,'Ax','Ay','ColorVariable','Az');

I am assuming values must be discretized in order plot them into a heatmap, however I am unsure how to discretize Ax,Ay, and Az properly to produce an accurate heatmap of my imported data.

Jyothis Gireesh 2019-11-22