How to add columns of accumulated sum in a matrix

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Philippe Corner
Philippe Corner 2018-1-23
评论： Star Strider 2018-1-24
If a have this matrix:
A=[1:1:100]
B=[101:1:200]
M=[A(:), B(:)]
I need to add 20 columns to M which contain the summation of A values like:
C = summation of the row |i| + the row |i-1|,
D = summation of the row |i| + the row |i-1|+|i-2|,
E = summation of of the row |i| + the row |i-1|+|i-2|+|i-3|,.. etc
and M=[A(:), B(:), C(:), D(:), E(:) ...etc]
For example: it would be something like:
A B C D E.. etc -> until 20
1 101 1 1 1
2 102 3 3 3
3 103 5 6 6
4 104 7 9 10
5 105 9 12 14
6 106 11 15 18
7 107 13 18 22
8 108 15 21 26
9 109 17 24 30
10 110 19 27 34
11 111 21 30 38
12 112 13 33 42
. . . . .
. . . . .
. . . . .
etc etc etc etc etc ... etc -> until 20
  2 个评论
Star Strider
Star Strider 2018-1-23
Note: this is not homework. It’s meteorology or climatology research.
Philippe Corner
Philippe Corner 2018-1-23
Yep, im trying to analyze some climate data. But for my bachelor thesis. I already did a cumsum, but there are too many columns, so im looking for a more automatic way to do it..
Thanks in advance Mr Star.

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采纳的回答

Star Strider
Star Strider 2018-1-24
This seems to work for ‘C’, ‘D’ ... ‘T’.
This construction seems the only way to form your matrix (that I call ‘Ar’ here).
A = (1:100)';
Ar(1,:) = ones(1, 20);
for k1 = 2:numel(A)
if k1 <= 20
v1 = cumsum(A(k1:-1:max(1,k1-19)));
Ar(k1,:) = [v1(2:end)' v1(end)*ones(1, 21-k1)];
else
v1 = cumsum(A(k1:-1:1));
Ar(k1,:) = v1(2:21)';
end
end

更多回答（1 个）

Image Analyst
Image Analyst 2018-1-23
Sounds like homework. See if you can figure out how to use the cumsum() function to do it. Let us know if you really can't figure it out.
  1 个评论
Philippe Corner
Philippe Corner 2018-1-23
I already did with cumsum(), but im trying to figure it out with more columns and im trying to automatize the code for that.

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