The randMat() command generates a random matrix: randMat(rows,columns) generates a rows by columns matrix whose entries are random integers between -9 and 9.
:RandSeed 0 :randM(3,2) [4 -2] [0 -7] [8 8 ]
Using the RandSeed command makes the random matrix entirely predictable: after setting the random seed to some value, the same random matrix will be returned every time (assuming the size is the same). See the RandSeed page for details of how random numbers are generated.
260 - Domain error happens when the rows and columns parameters aren't positive integers..