matlib (version 0.9.8)

rowmult: Multiply Rows by Constants

Description

Multiplies one or more rows of a matrix by constants. This corresponds to multiplying or dividing equations by constants.

Usage

rowmult(x, row, mult)

Value

the matrix x, modified

Arguments

x

a matrix, possibly consisting of the coefficient matrix, A, joined with a vector of constants, b.

row

index of one or more rows.

mult

row multiplier(s)

See Also

echelon, gaussianElimination

Other elementary row operations: rowadd(), rowswap()

Examples

A <- matrix(c(2, 1, -1,
             -3, -1, 2,
             -2,  1, 2), 3, 3, byrow=TRUE)
b <- c(8, -11, -3)

# using row operations to reduce below diagonal to 0
Ab <- cbind(A, b)
(Ab <- rowadd(Ab, 1, 2, 3/2))  # row 2 <- row 2 + 3/2 row 1
(Ab <- rowadd(Ab, 1, 3, 1))    # row 3 <- row 3 + 1 row 1
(Ab <- rowadd(Ab, 2, 3, -4))
# multiply to make diagonals = 1
(Ab <- rowmult(Ab, 1:3, c(1/2, 2, -1)))
# The matrix is now in triangular form