How can I extract values from a histogram (figure)?

Hi everyone,

Since I am very new to MatLab and will be needing it for my analysis in the coming days, I was hoping that someone could help me out.

I have a histogram (figure format), but I don't know how to extract the y-values (probability) of each bar and put it either into a list / excel file.

Could someone help me out here?

Thank you!

[KALYAN ACHARJYA]

Have you generated this figure in Matlab?

Or you just have the figure file only.

[Ola Zurek]

This figure was generated in Matlab (i didn't write the script, just loaded a picture when running the program).

[the cyclist]

It's important to know exactly what you imported. For example, was it a *.fig file, that you loaded into MATLAB via the openfig command?

[Ola Zurek]

The histogram was generated by the given script and the output was the histogram in (.fig) file (attached).

[Adam Danz]

If you have access to the script and the input data, you can (and should) get the histogram values from the script rather than from the figure.

Answer 1

[Adam Danz]

If you have access to the script/function that produced the histogram and the input data, you should get the histogram values from within the code. Find this line of code:

histogram(..., ...)

If you only have the figure and you need to extract the histogram values, here's how.

axisHandle = gca;                         %handle to the axis that contains the histogram
histHandle = axisHandle.Children;         %handle to the histogram
histData = histHandle.Data;               %The first input to histogram()
binEdges = histHandle.BinEdges;           %The second input to histogram() (bin edges)

% Reproduce the figure
figure
histogram(histData, binEdges)

% If you're looking for the height of each bar:
barHeight = histHandle.Values; 

For more information about what's stored in 'histHandle': https://www.mathworks.com/help/matlab/ref/matlab.graphics.chart.primitive.histogram-properties.html

Answer 2

[Steven Lord]

If you only have access to the figure file, use openfig to open it in a figure window then use findobj to obtain the handle of the histogram. Once you have the handle of the histogram, retrieve its properties like Values as Adam Danz showed.

Create a sample histogram for purposes of demonstrating findobj.

x = randn(1, 1e5);
histogram(x)

Find the histogram in the current figure.

h = findobj(gcf, 'Type', 'histogram');

Retrieve the Data of the histogram and compare it to the data originally used to create it.

data = h.Data;
isequal(data, x) % true

Look at the other properties of the histogram.

disp(h)

[Adam Danz]

@Ola Zurek, Steven Lord's suggestion to get the object handle using findobj() is safer than my suggestion to access the axes' children since there could be more than 1 object plotted on the axes.

[Steven Lord]

And if you're running code to create the histogram and retrieve the bin counts but you don't actually need or want the figure, instead you can call histcounts which will return just the counts and edges. It might not even require a lot of changes to your code since histcounts accepts most or all of the non-graphics options that histogram accepts.