Thread Subject: how to plot the distribution of 2d-dct coefficients

hello, everybody
      i want to plot the distribution of 2d-dct coefficients in
matlab. First, i use 'blkproc' fucntion to complete the block dct
transform for one image, and then i want to use 'hist' to plot the
distribution of coefficients which have the same location in all
blocks. The problem is that I don't know how to decide the second
parameter of hist function, inluding the length and the interval.
Because the max value of coefficients is different for different
locations in one block and also for various images.