MATLAB: How to do such a “averageifs”(excel) process in Matlab

accumarrayMATLABsumif

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.

Best 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)
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