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How can I do such a "averageifs"(excel) process in Matlab?

Asked by jee young yoo on 16 Aug 2019
Latest activity Commented on by jee young yoo on 16 Aug 2019
Hello,
How can I perform "sumifs" process in Matlab?
for example,
x1 = [ 201901, 201901, 201901, 201902, 201902, 201902, 201903, 201903, 201903], array, timetable
y1 = [1.52, 1.23, 1.42, 1.46, 2.42, 2.35, 3.24, 3.21, 3.44], array, double.
I'd like to do average [201901, 201902, 201903] and create new varaible with
x2 = [201901, 201902, 201903]
y2 = [x.xx, y.yy, z.zz]
? I've check some answers with accumarray function but it is still hard to understand.
Many thks.

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1 Answer

Answer by Rik
on 16 Aug 2019
Edited by Rik
on 16 Aug 2019
 Accepted Answer

Using accumarray is probably better, but you can also use the unique function and a for loop to find the sum and the count.
Edit:
I already gave you some pointers you could have tried. Everyone starts out by trying random things until it works. But the code below shows both methods.
x1 = [ 201901, 201901, 201901, 201902, 201902, 201902, 201903, 201903, 201903];
y1 = [1.52, 1.23, 1.42, 1.46, 2.42, 2.35, 3.24, 3.21, 3.44];
x_method_1=unique(x1);
y_method_1=zeros(size(x_method_1));
for n=1:numel(y_method_1)
%you could also find the count with sum(L) and the sum with sum(y1(L))
L=ismember(x1,x_method_1(n));
y_method_1(n)=mean(y1(L));
end
[x_method_2,~,ic] = unique(x1);
y_method_2=accumarray(ic,y1,[],@mean);
y_method_2=reshape(y_method_2,size(x_method_2));
%confirm the methods are equivalent
assert(max(abs(y_method_2-y_method_1))<2*eps)

  2 Comments

Yes, that maybe.. but the reason why I write question in detail is to know how to perform the command exactly, as I am a beginner in Matlab. Thanks for your time.
I am working on this problem 4 hours now. But your solution helped..! Thanks! :)

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