Language Reference

EXPMATRIX Function

EXPMATRIX (matrix) ;

This function is supported by the IML procedure and the iml action.

The EXPMATRIX function is part of the IMLMLIB library. Given an n times n matrix A, the EXPMATRIX function returns an n times n matrix approximating e Superscript upper A Baseline equals sigma-summation Underscript k equals 0 Overscript normal infinity Endscripts StartFraction upper A Superscript k Baseline Over k factorial EndFraction. The function uses a Padé approximation algorithm as presented in Golub and Van Loan (1989).

Note that this module does not exponentiate each element of a matrix; for that, use the EXP function.

The following example demonstrates the EXPMATRIX function. For the matrix used in the example, e Superscript t upper A is the matrix Start 2 By 2 Matrix 1st Row 1st Column e Superscript t Baseline 2nd Column t e Superscript t Baseline 2nd Row 1st Column 0 2nd Column e Superscript t Baseline EndMatrix period You can compute the exponential matrix as follows:

A = { 1 1, 0 1 };
t = 3;
X = ExpMatrix( t*A );
ExactAnswer = ( exp(t) || t*exp(t) ) //
( 0      ||   exp(t) );
print X, ExactAnswer;

Figure 146: Matrix Exponential

X
20.08553760.256611
020.085537

ExactAnswer
20.08553760.256611
020.085537


Last updated: May 07, 2026