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Normalized histogram

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Normalized histogram


Arturo Serrano


28 Jan 2009 (Updated )

Same as histogram, but the area sum is 1.

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HISTNORM Histogram normalized
  [...] = HISTNORM(...) works like HIST, but the frequency is normalized so that area sum is 1.

  Bonus usage!
  [...] = HISTNORM(..., 'plot') plots and returns the output arguments. Be sure 'plot' is the last argument.

      data = randn(1)+randn(1)*randn (10000, 1);
      [xo,no] = histnorm(data, 101, 'plot');
      hold on
      plot (no, normpdf(no, mean(data), std(data)), 'r');
      hold off

  See also: HIST.

  Copyright 2009 DWTFYW.

MATLAB release MATLAB 7.7 (R2008b)
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Comments and Ratings (22)
22 Nov 2014 ?


10 Jul 2013 R


it work fantastic:)how could we use histnorm to calculate normalized histogram for hsv histogram

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10 Jul 2013 R


10 Jul 2013 R


26 Apr 2013 Damien



25 Mar 2013 arnold


nice one, thanks!

22 Mar 2013 Arturo Serrano

Arturo Serrano

The *area* must sum up to 1.
Thanks for rating!

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21 Mar 2013 Linpeng


The columns sum up to 10 instead of 1. Any ideas?

13 Mar 2013 Arturo Serrano

Arturo Serrano

*Why* is not working? I don't see any problems. Maybe if you give some clues, we can help.

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12 Mar 2013 Bernoulli Lizard

Bernoulli Lizard

This does not work. The height of my bins is on the order of 10^4. What is wrong?

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22 Jun 2012 ww


Fantastic :)

04 Sep 2011 Flavio Prattico

Flavio Prattico


18 Aug 2011 Bob


disregard above comment about the mean...

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18 Aug 2011 Bob


Doesn't seem to work with non-zero mean data sets. I found that the code below works better. It can not handle the case where you specify your own bin widths. But it can handle a matrix of data.
e.g.: histnorm([randn(1e3,1) randn(1e3,1)+8],50)

function varargout = histnorm(varargin)

len = size(varargin{1});
n = len(2);
[xo,no] = hist (varargin{:});
binwidths = diff(no);
xonorm = xo/sum (xo .* (binwidths(1)*ones(size(xo))))*n;

13 Oct 2010 Anne Calder

Anne Calder

Thank you! Works perfect!

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04 Oct 2010 Arturo Serrano

Arturo Serrano

Hi Anne,
you can change the colors by setting properties from the matlab command window. This should does the trick:

>> set (findobj (gca, 'type', 'patch'), 'edgecolor', [0.5 0.5 0.5], 'facecolor', [0.1 0.1 0.1]);

Edgecolor and facecolor values are the RGB values for bin colors (you can use letters also as plot does).

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03 Oct 2010 Anne Calder

Anne Calder

Super useful... was wondering if you can change the colors in the bins. This isn't working for me.

17 Jun 2010 Gustavo


05 Mar 2010 Shahzad Bhatti

Shahzad Bhatti

It didn't work for me. It is giving same histogram as does hist ... I mean it is not normlizing !!!

@ Author - Any idea - what i am doing wrong ?

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25 Feb 2010 Ian Baldwin

Ian Baldwin

very useful

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16 Nov 2009 abdelhamid alhassi

abdelhamid alhassi

thanks very helpful

20 Feb 2009 Darcy Sabatino

Darcy Sabatino

Very helpful. The histnorm() function is virtually as easy as the hist() function.

22 Mar 2013

Updated the example.

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