BBS: Inland Empire Archive Date: 05-02-92 (19:01) Number: 136 From: PAUL LEONARD Refer#: NONE To: RICHARD VANNOY Recvd: NO Subj: Matrix Conf: (2) Quik_Bas

On or about <May 01 19:40>, Richard Vannoy (1:105/314) scribbled: RV> MatrixA MatrixB MatrixC RV> 4 5 6 3 2 6 5 4 3 0 E M P T Y RV> 3 2 3 4 5 5 4 3 3 3 RV> 2 1 0 6 9 5 2 1 0 4 RV> so, something like... RV> MAT(C) = MAT(A) * MAT(B) (nit-picking mode on) My linear algebra's a bit rusty, but i don't think you can multiply the matrices in your example. If A is rA x cA (rA rows by cA columns), and B is rB x cB, then cA must equal rB in order to multiply the two matrices. This is because the elements of C are formed by multiplying the rows of A by the columns of B, with C being rA x cB (i learned this by thinking of the two equal dimensions needing to "canceling out"). This is why, in general, AB <> BA. AB is rA x cB and BA is rB x cA. (nit-picking mode off) (For Randy Baer) I was once put through the matrix multiplication wringer by a sadistic Fortran professor - he reacted rather badly to a negative student evaluation of his class and vengefully assigned a nasty stew of matrix manipulation (without MAT functions), statistical analysis and formatting. Anyway, the bare bones of the matrix multiplication are...DIMmat.a%(rA%,cA%)DIMmat.b%(rB%,cB%)DIMmat.c%(rA%,cB%)FORi%=1TOrA%FORj%=1TOcB%FORk%=1TOcA%'(or rB%)mat.c%(i%,j%) = mat.c%(i%,j%) + (mat.a%(i%,k%) * mat.b%(k%,j%))NEXTk%NEXTj%NEXTi% I also found a few more Basic-Plus2 MAT functions while digging through the on-line help trying to confirm the above. They are... DET - Returns determinant of a matrix NUM - Returns number of rows entered into a matrix with MATINPUTNUM2 - Returns number of elements in last row entered TRN - Creates the transpose of a matrix ptl --- msged 2.07 * Origin: PTL Pointwork (1:105/48.111)

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