How to differentiate the histogram ?

I have 3 types of histogram bar symetric,right skewed and left skewed.The problem here is how i can get the specific range that show the graph is really symetric,right skewed or left skewed.

%coding a = imread('e0.jpg'); b=rgb2gray(a);

[x,y]=size (b); c=b(1:1008,1:1280);

figure(1),imshow(c); imshow(c); figure(2), imhist(c) T2=graythresh(c); d=imhist(c); figure(3),plot(d)