cumulative sum of some columns of matrix

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Roisin Loughnane
Roisin Loughnane 2017-11-1
编辑： Roisin Loughnane 2017-11-1
I have a 100 x 12 matrix of monthly climate data values.
I want to create a matrix with the cumulative sum of the three previous months.
How can I use cumsum() to get the cumulative sum by row of a certain number of specified columns, not the whole row?

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KL
KL 2017-11-1
编辑：KL 2017-11-1
You seem to want to do cumsum along the second dimension, so trivial is to use
res = cumsum(yourMat,2);
but this will produce the typical cumsum. If you want to add every 3 columns only for a specific row,
yourRow = someval; %within your dimension range
cs = 1:size(yourMat,2);
cs1 = [1 1 cs(1:end-2)];
res = arrayfun(@(x,y) sum(yourMat(yourRow,x:-1:y)), cs, cs1, 'uni',0);
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KL
KL 2017-11-1
编辑：KL 2017-11-1
Ah yeah, I made some changes to my answer. Note that, it's only for a specific row (yourRow). For all the rows, from the top of my head, I'd superimpose it with another arrayfun. It doesn't look very elegant but still works for you.
res = arrayfun(@(z) arrayfun(@(x,y) sum(yourMat(z,x:-1:y)), cs, cs1, 'uni',0),1:yourRow,'uni',0)
Roisin Loughnane
Roisin Loughnane 2017-11-1
编辑：Roisin Loughnane 2017-11-1
It worked, thank you very much!
I used your code to loop over each row:
sst = table2array(sst(:,6:end));
res = zeros(size(sst));
for i = 1:length(sst)
cs = 1:size(sst,2);
cs1 = [1 1 cs(1:end-2)]; % 1 1 : 10
res(i,:) = arrayfun(@(x,y) sum(sst(i,x:-1:y)), cs, cs1);
end

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Birdman
Birdman 2017-11-1
编辑：Birdman 2017-11-1
A=randi([1 10],100,12)
A(:,2:5)=(cumsum(A(1:100,2:5)')')
This two lines does the trick.

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