Difference Matrix

Builds the matrix that takes the column-wise difference of another matrix when post-multiplied.

Description

 D = diffMat(obs,type)

Creates a difference matrix, D, that when multiplied by by another matrix takes its difference over obs columns. The type is either 'circular' or 'none'. The defalt is 'none'.

 EXAMPLE
 B = [2:1:8;sin(linspace(0,pi,7))]
 B =
     2.0000 3.0000 4.0000 5.0000 6.0000 7.0000 8.0000
          0 0.5000 0.8660 1.0000 0.8660 0.5000 0.0000

 D = diffMat(size(B,2));
 B*D
 ans =
    -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000
    -0.5000 -0.3660 -0.1340 0.1340 0.3660 0.5000

 B*diffMat(size(B,2),'circular')
 ans =
    -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 6.0000
    -0.5000 -0.3660 -0.1340 0.1340 0.3660 0.5000 0.0000

• MATLAB release: MATLAB 7.8 (R2009a)