Average of 3d matrix

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mohamad shirgholami
mohamad shirgholami 2020-12-14
编辑： KALYAN ACHARJYA 2020-12-14
hi
I have 3D matrix with dimension (61,57,365) the 365 is daily time. I want to do a monthly average overtime to get (61,57,12). But the number of days each month is different. I would be grateful for your help

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KALYAN ACHARJYA
KALYAN ACHARJYA 2020-12-14
编辑：KALYAN ACHARJYA 2020-12-14
#One Way
m=cumsum([0,31,28,31,30,31,30,31,31,30,31,30,31]);
data=rand(61,57,365); %Sample Data
month_ave=zeros(1,12)
for i=1:12
data1=data(:,:,m(i)+1:m(i+1));
month_ave(i)=mean(data(:));
end
month_ave
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KALYAN ACHARJYA
KALYAN ACHARJYA 2020-12-14
Mohmad comments moved here
hi
What do you mean by index?
if index=[31,28,31,30,31,30,31,31,30,31,30,31] , all arrays of output matrix become zeros.
thanks.
KALYAN ACHARJYA
KALYAN ACHARJYA 2020-12-14
编辑：KALYAN ACHARJYA 2020-12-14
In this case it added 2 more loops,definitely which isn't an efficient/easiest way out.
m=cumsum([0,31,28,31,30,31,30,31,31,30,31,30,31]);
data=rand(61,57,365); %Sample Data
ave_data=zeros(61,57,12);
for r=1:61
for c=1:57
for d=1:12
data1=data(r,c,m(d)+1:m(d+1));
ave_data(r,c,d)=mean(data1(:));
end
end
end
ave_data

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更多回答（1 个）

Walter Roberson
Walter Roberson 2020-12-14
Ran in:
%Sample Data
data = rand(61,57,365);
data(:,:,200:250) = 0;
%the work
m = cumsum([0,31,28,31,30,31,30,31,31,30,31,30,31]);
month_ave = zeros(size(data,1), size(data,2), 12);
for month = 1 : 12
start_at = m(month)+1;
end_at = m(month+1);
month_ave(:,:,month) = mean(data(:,:,start_at:end_at), 3);
end
%show results
format long g
mat2str( reshape(month_ave(1,1,:),1,[]) )
ans = '[0.522259150104234 0.461364358148672 0.471978553723879 0.528354847707762 0.522092627671028 0.424906953694024 0.29348062051905 0 0.382149020541875 0.38378942552417 0.454583006879377 0.543602194085556]'
Yup, the zero due to the gap I wrote into the data does show up in the result.

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