How to create a histogram plot with unequal bins?

LS,

I would like to generate a histogram plot for a dataset which is like:

a= [-99999999 -2 -2 -2 -1 -1 0 0 0 1 1 2]

When I use the normal hist function

hist(a)

only two bars are shown; one for the outlying value and one for the values around zero. The details of the values around zero disappear in the graph. Is there a way to avoid this? Can I generate bins from -2 to 2 and a separate bin for everything smaller than -3?

Your help is really appreciated.

Best regards,

Frits Hermans

Answer 1

[Laura Proctor]

b = -3:2;       % specify bin centers
n = hist(a,b)   % generate numbers to populate bins
bar(b,n)        % plot the resultant histogram

[Frits]

Hi Laura,

Thanks a lot for your answer.

Your code works fine except that it does not take into account the large negative value is put in the -2 bin. Is there a possibility to put that value in a separate bin dedicated to values less than -2? The purpose is to count real outliers.

Thanks for your help!

[the cyclist]

In your case, I think you probably want to use histc(), not hist(). Then, you can specify that you want your first (left-most) bin edge to be -2.

Then, set the XLim property such that you see only the extent of the plot that you want to.

[Walter Roberson]

Specify the first bin as negative infinity to catch all of the outliers.

Answer 2

[the cyclist]

You can specify the bins precisely, using either the hist() or histc() functions. May I recommend a careful read of the documentation, which spells out how to do this.

>> doc hist
>> doc histc

Specifically, look at the syntax

 >> hist(Y,x)

which specifies the locations of the centers of the bins, or

 >> histc(Y,edges)

which specifies the locations of the edges.