MATLAB: How to define the bin size for a histogram

histogram

Hello

I have 2 questions.

I am trying to create 100 bins for my histograms which covers actually 10000 data points. The command bincounts = histc(x,binranges), allows me to put the binranges value but I dont want to repeat (0 100 200……….10000)as the value for 'binranges'. So is there any shorter way to give that kind of argument for binranges to use that command. Once I know that, I can use bar(binranges,bincounts,'histc') to plot the histogram.

Second question, how do I normalize the area of the histogram to be 1.

Thanks

Best Answer

There are two histogram functions in matlab. The other one, hist allows you to specify the number of bins instead of the edges.

As for normalising:

dist = hist(data, 100);
dist = dist / sum(dist);

Related Solutions

MATLAB: Finding the edges of equally distanced bins

[counts,centers] = hist(data, nBins);

So you know the centers. And that means you know the width

binWidth = centers(2)-centers(1)

So the left most edge is just centers - binWidth/2 and the right most edge is centers(end)+binWidth/2, or overall it should be

edges = [centers-width/2, centers(end)+binWidth/2];

MATLAB: Normalized distribution for histogram

If you have the Statistics Toolbox, you might find the dfittool distribution fitting tool quite useful.

doc dfittool

If not, you can normalize a histogram by scaling the counts in each bin. With the normalized counts, you can plot both the normalized histogram and your curve. The trick is to identify the appropriate scaling factor.

Here is some example code where I plot the normal probability with the normalized histogram data:

% Arbitrary data generation and statistics
dataVec = randn(1000,1);
muData = mean(dataVec);
stdData = std(dataVec);
% Defining the bin centers
binStep    = 0.1;
binCenters = -5:binStep:5;
% Compute the histogram scaling factor. (If all histogram counts are in a
% single bin, the probability = 1)
binCount   = histc(dataVec,binCenters);
probScale  = sum(binCount)*binStep;
% Plot the normalized histogram and change the bar color for line
% visibility
histHandle = bar(binCenters,binCount/probScale,'hist');
set(histHandle,'FaceColor',[1,1,1]); 
hold on;
% Overlay the distribution fit on the histogram
x = binCenters;
y = normpdf(x,muData,stdData);
plot(x,y);
xlabel('Data');
ylabel('Probability');

Hope this helps to get you started!

Best Answer

Related Solutions

MATLAB: Finding the edges of equally distanced bins

MATLAB: Normalized distribution for histogram

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