HP 15c - Manual (Page 147)

Section 12: Calculating with Matrices 147
Example: Recall the element in row 2, column 1 of matrix A from the
previous example. Use the stack registers.
Keystrokes Display
2 v 1
1
Enters row number into Y-
register and column number into
X-register.
l | A 4.0000
Value of a
21
.
Storing a Number in All Elements of a Matrix
To store a number in all elements of a matrix, simply key that number into
the display, then press O> followed by the letter key specifying
the matrix.
Matrix Operations
In many ways, matrix operations are like numeric calculations. Numeric
calculations require you to specify the numbers to be used; often you define
a register for storing the result. Similarly, matrix calculations require you to
specify one or two matrices that you want to use. A matrix descriptor is
used to specify a particular matrix. For many calculations, you also must
specify a matrix for storing the result. This is the result matrix.
Because matrix operations usually require many individual calculations, the
calculator flashes the running display during most matrix operations.
Matrix Descriptors
Earlier in this section you saw that when you press l > followed
by a letter key specifying a matrix, the name of the matrix appears at the left
of the display and the number of rows followed by the number of columns
appears at the right. The matrix name is called the descriptor of the matrix.
Matrix descriptors can be moved among the stack and data storage registers
just like a number – that is, using O, l, v, etc. Whenever a
matrix descriptor is displayed in the X-register, the current dimensions of
that matrix are shown with it.
You use matrix descriptors to indicate which matrices are used in each
matrix operation. The matrix operations discussed in the rest of this section