- in your array A, A(1:8) belong to the same number, A(9:16) to another mother, etc..
- There are N mothers and, hence, N*8 elements in A.
- A(k).Value is a scalar

# Search all strings occuring in structure

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I have a structure called A (as attached) with the fields Mother, SampleName and Value. Every eight variables SampleNames belong to the same Mother, which is coded in the name (e.g. Mother: 'cutTDM100_111_111_111_111_000' and SampleName: 'cutTDM050_111_111_111_111_122'). I would like to sum up the eight values that each belong to the same Mother. I tried a loop using strcmp, but there is something wrong and it keeps on adding even after the eight value.

sum_value = zeros (3,3)

for k=1:length(A)

while strcmp(A(k+1).Mother,A(k).Mother)

value_add= (A(k).value)

sum_value= sum_value + value_add

end

end

This is probably not the most elegant solution anyways and some index for the output would have to be added. Another thing I could think of, is extracting all the occuring Mother Names and write a loop based on this. However, I could not figure out how to search all the strings occuring withing the structure. Getfield only returns one name.

getfield(A(n), 'Mother')

##### 0 Comments

### Accepted Answer

Jos (10584)
on 25 Mar 2016

So, I assume:

AllValues = [A.Value]

AllValues = reshape(AllValues,8,[]) % a 8-by-N array

SumValue = sum(AllValues,1) % sum each row

Note that this is not very flexible ...

##### 3 Comments

Jos (10584)
on 25 Mar 2016

Aha, we can concatenate and sum in higher dimensions! This might then work:

AllValues = cat(3,A.Value) % a 3x3x(N*8) array

AllValues = reshape(AllValues,3,3,[],8) % a 3-3-N-by-8 array

SumValue = sum(AllValues,4) % a 3x3xN matrix

It could be that I switch the N and the 8, so you have to check!

### More Answers (2)

Guillaume
on 24 Mar 2016

Edited: Guillaume
on 25 Mar 2016

If I understood correctly this should do what you want:

mothers = {A.Mother}; %concatenate all Mother fields into a cell array of string

[mother, ~, subs] = unique(mothers); %identify identical mothers

sum_value = accumarray(subs, [A.value]); %sum (default function of accumarray) all values belonging to identical mothers

Note that sum_value is in the same order as mother which is alphabetical. If you prefer them to be in the same order as the values occur in the structure, add the 'stable' option to unique.

Also note that sum_value is the sum of all the values for an identical mother, if you want to restrict it to at most 8 values (and discard the rest?) then:

sum_value = accumarray(subs, [A.value], [], @(v) sum(v(1:min(8, end))));

edited for incorrect order in the arguments of accumarray

##### 4 Comments

Guillaume
on 25 Mar 2016

Since you've confirmed that the value field is not scalar, it's probably simpler to forget about accumarray. You'd still start with unique:

[mothers, ~, subs] = unique({A.Mother});

sum_value = cell(size(mothers));

for mother_idx = 1:numel(mothers)

values = {A(subs == mother_idx)};

sum_value{mother_idx} = sum(cat(3, values{:}), 3);

end

If you only want to sum a maximum of 8 values per unique mothers, then replace the sum line with:

sum_value{mother_idx} = sum(cat(3, values{1:min(end, 8}), 3);

Walter Roberson
on 24 Mar 2016

##### 4 Comments

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