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# how to obtain the number of cases of length. but those matrices sum must be 30 or something value(on constraints)

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Brian Kim on 13 Sep 2017
Closed: MATLAB Answer Bot on 20 Aug 2021
first, -constraints-
elements must be between 4 and 12
for example,
A=[6 7 8 9], sumA=sum(A)=30;
What is number of cases of length that can be obtained so that the sum becomes 30?
For reference,
If the length of the matrix is 5, A is [5 5 6 7 7].
Walter Roberson on 13 Sep 2017
Stephen, you should not close duplicate questions that have Answers unless the Answers also appear in the original location.

KSSV on 13 Sep 2017
x0 = 4 ; x1 = 12 ;
x = x0:x1 ;
iwant = cell([],1) ;
count = 0 ;
for i = 1:length(x)
A = nchoosek(x,i) ;
thesum = sum(A,2) ;
if any(thesum==30)
count = count+1 ;
iwant{count} = A(thesum==30,:) ;
end
end
You have the possible combinations whose sum is 30 in iwant.
Brian Kim on 13 Sep 2017
ah~ i am sorry. i mean, some of elements can be same.

Walter Roberson on 13 Sep 2017
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Walter Roberson on 13 Sep 2017
If you just need to calculate the number of different ways that you can partition a number with particular (possibly repeated) integers, then see the mathematics outlined at https://math.stackexchange.com/questions/15521/making-change-for-a-dollar-and-other-number-partitioning-problems

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