How to build a continuous 2D counting histogram in Matlab

Hello all ,
I have a problem, hope anyone could help me. Here it is:

1- i analysed all speech frames using a filterbank of 4 subbands.
2- for each subband i, I calculated 2 continuous features say x1 and
x2.

I am required to build a 2D counting histogram for each subband i.
The two axes of this histogram are:
(a) the range of values of x1 observed in subband i which is in the
range [-36,36]bin.
(b)the range of values of x2 observed in subband i which is in the
range [-51,51] bin.

It counts the number of frames observed for each (x1,x2) combination
in a certain subband i.

The question is:
How can i build such a 2D counting histogram? Should i use a gaussian
mixture to approximate the required histogram? Is there any ready
made matlab code or toolbox that eases the building of this
histogram?
Thanks alot
.

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