MATLAB: Fit a histogramm to a gaussian- or vice versa

gaussianhistogram

Hello folks.

After making a histogramm, i want to compare it with the bell curve. But i have difficulties to manage a fit.

For calculating the bell curve i'm using this function:

function f = gauss_distribution(x, mu, s)
p1 = -.5 * ((x - mu)/s) .^ 2;
p2 = (s * sqrt(2*pi));
f = exp(p1) ./ p2;

What can i do to make them fit? I'm really frustrated right now. Is there a good way?

Greetings

Best Answer

One thing you'll need to do is to scale the histogram and bell curve so they have the same area. See my answer to this question:

http://www.mathworks.com/matlabcentral/answers/29598-histogram

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MATLAB: How to create a plot with a histogram in the same graph

The histogram is the distribution. Please explain. If you want to plot a curve - some curve representing the theoretical distribution rather than the actual distribution like what the histogram is, then call "hold on" after you call bar() to plot your histogram and before you call plot() to plot the curve:

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% Demo to plot histogram and cdf of grayscale image.
% By ImageAnalyst
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close all;  % Close all figures (except those of imtool.)
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fontSize = 14;
% Read in a standard MATLAB gray scale demo image.
folder = fullfile(matlabroot, '\toolbox\images\imdemos');
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% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
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title('Grayscale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
set(gcf,'name','Demo by ImageAnalyst','numbertitle','off') 
% Let's compute and display the histogram.
[pixelCount grayLevels] = imhist(grayImage);
subplot(2, 2, 2); 
bar(pixelCount);
title('Histogram of image', 'FontSize', fontSize);
xlim([0 grayLevels(end)]); % Scale x axis manually.

grid on;
% Compute the CDF
cdf = cumsum(pixelCount) / numel(grayImage);
% Plot both hist and cdf on same plot
subplot(2,2,3);
bar(pixelCount);
hold on;
z = zeros(1,length(pixelCount));
plotyy(grayLevels, z, grayLevels, cdf);
title('Histogram and CDF of image', 'FontSize', fontSize);
xlim([0 grayLevels(end)]); % Scale x axis manually.
grid on;

Best Answer

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