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Row subtraction in matrix

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Ian Loveless
Ian Loveless 2018-5-23
评论： Ian Loveless 2018-5-25
I am trying to subtract each row in a matrix from the row after it. The function diff does x_{i} - x_{i+1}, I need to do x_{i}-x_{i-1}. I cannot find anything that will tell me how to do this. I am sure it is something simple that I am just overlooking.
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Stephen23
Stephen23 2018-5-23
The diff help states that for a matrix it returns
[X(2,:)-X(1,:); X(3,:)-X(2,:); ... X(p,:)-X(p-1,:)]
which seems to match what you asked for.
Ian Loveless
Ian Loveless 2018-5-23
Then I mistyped. Is there a way I can do row{i}-row{i+1}?

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回答（1 个）

James Tursa
James Tursa 2018-5-23
编辑：James Tursa 2018-5-23
Just negate the usual diff() result. E.g.,
x = your matrix
result = -diff(x);
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Stephen23
Stephen23 2018-5-24
编辑：Stephen23 2018-5-24
"It is the same as my diff() matrix, except each value has "-" in front of it."
That would be exactly correct then. The only difference between these
row(i)-row(i+1)
row(i)-row(i-1)
will be the sign. So if all were positive in the first case, then in the second case all would be negative.
Ian Loveless
Ian Loveless 2018-5-25
You are all correct, I apologize for my ignorance. I was looking at spacings instead of differences. Thank you for your help and patience.

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