logm square matrix logarithm

## Syntax

    y=logm(x)

## Arguments

x

  square matrix

## Description

`logm(x)` is the matrix logarithm of `x`. The result is complex if `x` is not positive or definite positive. If `x` is a symmetric matrix, then calculation is made by Schur form. Otherwise, `x` is assumed diagonalizable. One has `expm(logm(x))=x`.

## Examples

    A=[1,2;3,4];
    logm(A)
    expm(logm(A))

    A1=A*A';
    logm(A1)
    expm(logm(A1))

    A1(1,1)=%i;
    expm(logm(A1))

## See also

- expm
- log