# how to call out single element in matrix

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Noriham B on 29 Jul 2022
Commented: Walter Roberson on 29 Jul 2022
Dear Prof/Dr./Sir./Maam
I have matrix A=[1 2 3 4 5 6 ] and B=[ 7 8 9]. I want to calculate s1=1+2+7 s2=3+4+8 s3=5+6+9
Is it possible to calculate the elements from different matrix like that?

Walter Roberson on 29 Jul 2022
A(1:2:end) + A(2:2:end) + B
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Walter Roberson on 29 Jul 2022
MATLAB has an operator that it calls "colon" that is available in two forms.
A:B
means the sequence of values starting from A, and add one each time, ending with the last number that is not greater than B. So for example 2.1:4 would be 2.1 then 3.1 and then when it internally looked at 4.1 it would be greater than the 4 endpoint so that sequence would stop with just the two values.
A:B:C
is closely related. If B is positive then you start from A, add B each step, and end before exceeding C. If B is negative such as 5:-1:3 then you add B each step (so you are subtracting) but you end when the result would be less than C, so 5:-1:3 would be 5 4 3
1:2:end thus means starting at 1 and add 2 each time, so 1 3 5 and so on. The "end" in A(1:2:end) stands in for the maximum index for that array. With A being 6 long A(1:2:end) would be A(1:2:6) which would be A([1 3 5]) . A(2:2:end) with length 6 would be A(2:2:6) or A([2 4 6])

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