How do I create such matrix ? (please look at the thread for further details)

Hi,

Let say I have a matrix of m column. eg[X1 X2 X3 X4 ... Xm].

How do I create a matrix that becomes [X1 X2-X1 X3-X2 X4-X3 ... Xm-Xm-1]for m columns ?

And if I have n rows and m column, how do I create such matrix?

Answer 1

[Azzi Abdelmalek]

v=[10 50 200 1000]
out=[v(1) diff(v)]

[Azzi Abdelmalek]

v=[10 50 200 1000;1 5 20 100]
out=[v(:,1) diff(v,[],2)]

Answer 2

[Image Analyst]

Alternative ways that could be extended for subtracting more than 2 columns, but Azzi's method is probably better/simpler/easier to understand for subtracting just 2 columns.

outc =  [v(1),   conv(v, [1,-1],  'valid')] % 1D
outc2 = [v(:,1), conv2(v, [1,-1], 'valid')] % 2D