Signature File format

Can someone verify the format of the sig files created by i.gensig,etc?

I beleive they are:

#cat
num
u1 u2 u3
S(x1-u1)(x1-u1)
S(x1-u1)(x2-u2) S(x2-u2)(x2-u2)
S(x1-u1)(x3-u3) S(x2-u2)(x3-u3) S(x3-u3)(x3-u3)

where

cat Each catagory in training set
num total number of pixels in cat
u? mean for rast ?
x? each rast ? value
S()() Summation over all pixels in cat

Thanks in advance

Quinn Hart (qjhart@ucdavis.edu)
Dept. Land, Air, and Water Resources
UC Davis