HP 15c Scientific ´ m, rows, columns, number of, number of, Dimensioning a Matrix, Key the number of rows, Section 12: Calculating with Matrices

Section 12: Calculating with Matrices 141

Matrix inversion, for example, can be performed on an 8×8 matrix with real elements (or on a 4×4 matrix with complex elements, as described later*).

To conserve memory, all matrices are initially dimensioned as 0×0. When a matrix is dimensioned or redimensioned, the proper number of registers is automatically allocated in memory. You may have to increase the number of registers allocated to matrix memory before dimensioning a matrix or before performing certain matrix operations. Appendix C describes how memory is organized, how to determine the number of registers currently available for storing matrix elements, and how to increase or decrease that number.

Dimensioning a Matrix

To dimension a matrix to have y rows and x columns, place those numbers in the Y- and X-registers, respectively, and then execute ´ m followed by the letter key specifying the matrix:

1.Key the number of rows (y) into the display, then press v to lift it into the Y-register.

2.Key the number of columns (x) into the X-register.3.Press ´ m followed by a letter key, A through E,that specifies the name of the matrix.†

Y

X

number ofrows

number of

columns

*The matrix functions described in this section operate on real matrices only. (In Complex mode, the imaginary stack is ignored during matrix operation.) However, the HP-15C has four matrix functions that enable you to calculate using real representations of complex matrices, as described on pages 160-173.

†You don't need to press ´before the letter key. (Refer to Abbreviated Key Sequences on page 78.)