how to do sum of element of multiple number in matlab?

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Putri Basenda Tarigan 2020-11-18

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评论： Putri Basenda Tarigan 2020-11-18

采纳的回答： Rik

Hello everyone.

If I have

m=[3 3 4 3 2 4 3]

c=[3 4]

then I want to calculate the sum of m(c) at the same time

I tried

b=1:m(c)

b=sum(b)

but only give me one number. I want it to be 2 numbers. How to do this?

Thanks in advance

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Timo Dietz 2020-11-18

Could you please explain in more detail? Does c contain the indices up to which you like to sum up m - starting always from 1? Or why do you expect two numbers as result?

Putri Basenda Tarigan 2020-11-18

this means that for c=3, I want to sum m from 1 to 3, so it's 10. and for c=4, it's sum of m from 1 to 4, so it's 13.

then I want to achieve these two numbers to compare them in the next step

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Rik 2020-11-18

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在 MATLAB Online 中打开

b=cumsum(m);
b=b(c);

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Timo Dietz 2020-11-18

That's intersting. Many thanks for the insights.

Putri Basenda Tarigan 2020-11-18

Thank you Sir

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Timo Dietz 2020-11-18

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编辑：Timo Dietz 2020-11-18

在 MATLAB Online 中打开

Not sure whether I got your issue. But in case you want to summarize all members of m starting at index 1, up to each member of c (containing indices of m) individually, you can do this:

b=arrayfun(@(x) sum(m(1:x)), c)

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Rik 2020-11-18

Functions like arrayfun and cellfun tend to be slower than using a for loop. The exception appears to be the legacy calls of cellfun (so those with the char input, instead of a function handle).

Timo Dietz 2020-11-18