MATLAB Release Notes |

**Mathematics Upgrade Issues**

The issues involved in upgrading from MATLAB 6.1 to MATLAB 6.5, in terms of mathematics features, are discussed below.

**Singular Triangular Matrix Division **

The result of dividing a singular lower or upper triangular matrix by any other matrix, using either left (`\`

) or right (`/`

) division may change. Previously, for singular square matrices `A`

for which `rcond(A) = 0`

, the result was always a matrix of `Inf`

s.

This change is a result of performance improvements described in Mathematics Features.

A = [1 2 3;0 4 5;0 0 0]; b = [1;2;3]; A\b Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND = 0.000000e+000. ans = NaN -Inf Inf

In MATLAB 6.5, a zero matrix is treated as a singular triangular matrix.

[0 0;0 0] \ [0 0]' Warning: Matrix is close to singular or badly scaled. Results may be inaccurate. RCOND = 0.000000e+000. ans = NaN NaN

Development Environment Upgrade Issues | Programming and Data Types Upgrade Issues |