nested loop will not enter second iteration

1 Jul 2017
1 Answer
Answer Accepted
Updated 1 Jul 2017
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Hi,
Below is my code. For each month of each year I am trying to get the average and std for a set of values. The first iteration works for the first year. But then it does not continue. Can someone tell me where the problem is.
[M,ia,ic] = unique(CO2_FFD(:,2)); %find unique years, M = unique year, ia = row with unique year
m=[1;2;3;4;5;6;7;8;9;10;11;12];%set an array for 12 months
CO2_YM_averages = zeros(length(M)*12,2); %array for averages & std's, size of year*12months
for i=1:length(M)
yrows = find(M(i)==CO2_FFD(:,2)); %find rows where year is equal to M(i)
for j=1:length(m)
mrows=find(CO2_FFD(yrows,3)== m(j));%find rows where month = m(i)
CO2_YM_averages(j,1) = mean(CO2_FFD(mrows,8)); %average data for each month
CO2_YM_averages(j,2) = std(CO2_FFD(mrows,8)); %std data for each month
end
end

4 Comments
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Image Analyst
Image Analyst on 1 Jul 2017
Undefined function or variable 'CO2_FFD'.
Please supply it so we can run your code.
Jennifer Walker
Jennifer Walker on 1 Jul 2017
It is an array of >30,000 rows but it is structured as
CO2_FFD = [ serial date, YY, MM, DD, HR, MIN, SEC, VALUE]
Jennifer Walker
Jennifer Walker on 1 Jul 2017
I can see that i is not incrementing when the code stops >> i
i =
1
Jennifer Walker
Jennifer Walker on 1 Jul 2017
here is some sample data:
CO2_FFD = [0 2000 1 1 0 0 0 340 ; 0 2000 1 2 0 0 0 380 ; 0 2000 2 3 0 0 0 280 ; 0 2000 2 4 0 0 0 450 ; 0 2000 3 5 0 0 0 330 ; 0 2000 3 6 0 0 0 450 ; 0 2000 4 7 0 0 0 380 ; 0 2000 4 8 0 0 0 290 ; 0 2000 5 9 0 0 0 340 ; 0 2000 5 10 0 0 0 380 ; 0 2000 6 11 0 0 0 280 ; 0 2000 6 12 0 0 0 450 ; 0 2000 7 13 0 0 0 330 ; 0 2000 7 14 0 0 0 450 ; 0 2000 8 15 0 0 0 380 ; 0 2000 8 16 0 0 0 290 ; 0 2000 9 17 0 0 0 340 ; 0 2000 9 18 0 0 0 380 ; 0 2000 10 19 0 0 0 280 ; 0 2000 10 20 0 0 0 450 ; 0 2000 11 21 0 0 0 330 ; 0 2000 11 22 0 0 0 450 ; 0 2000 12 23 0 0 0 380 ; 0 2000 12 24 0 0 0 290 ; 0 2001 1 25 0 0 0 340 ; 0 2001 1 26 0 0 0 380 ; 0 2001 2 27 0 0 0 280 ; 0 2001 2 28 0 0 0 450 ; 0 2001 3 29 0 0 0 330 ; 0 2001 3 30 0 0 0 450 ; 0 2001 4 1 0 0 0 380 ; 0 2001 4 2 0 0 0 290 ; 0 2001 5 3 0 0 0 340 ; 0 2001 5 4 0 0 0 380 ; 0 2001 6 5 0 0 0 280 ; 0 2001 6 6 0 0 0 450 ; 0 2001 7 7 0 0 0 330 ; 0 2001 7 8 0 0 0 450 ; 0 2001 8 9 0 0 0 380 ; 0 2001 8 10 0 0 0 290 ; 0 2001 9 11 0 0 0 340 ; 0 2001 9 12 0 0 0 380 ; 0 2001 10 13 0 0 0 280 ; 0 2001 10 14 0 0 0 450 ; 0 2001 11 15 0 0 0 330 ; 0 2001 11 16 0 0 0 450 ; 0 2001 12 17 0 0 0 380 ; 0 2001 12 18 0 0 0 290 ; 0 2002 1 19 0 0 0 340 ; 0 2002 1 20 0 0 0 380 ; 0 2002 2 21 0 0 0 280 ; 0 2002 2 22 0 0 0 450 ; 0 2002 3 23 0 0 0 330 ; 0 2002 3 24 0 0 0 450 ; 0 2002 4 25 0 0 0 380 ; 0 2002 4 26 0 0 0 290 ; 0 2002 5 27 0 0 0 340 ; 0 2002 5 28 0 0 0 380 ; 0 2002 6 29 0 0 0 280 ; 0 2002 6 30 0 0 0 450 ; 0 2002 7 31 0 0 0 330 ; 0 2002 7 32 0 0 0 450 ; 0 2002 8 33 0 0 0 380 ; 0 2002 8 34 0 0 0 290 ; 0 2002 9 35 0 0 0 340 ; 0 2002 9 36 0 0 0 380 ; 0 2002 10 37 0 0 0 280 ; 0 2002 10 38 0 0 0 450 ; 0 2002 11 39 0 0 0 330 ; 0 2002 11 40 0 0 0 450 ; 0 2002 12 41 0 0 0 380 ; 0 2002 12 42 0 0 0 290 ]

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 Accepted Answer

Image Analyst
Image Analyst on 1 Jul 2017

1 vote

I get 3 tierations for i. Here is my code:
% here is some sample data:
CO2_FFD = [0 2000 1 1 0 0 0 340 ;
0 2000 1 2 0 0 0 380 ;
0 2000 2 3 0 0 0 280 ;
0 2000 2 4 0 0 0 450 ;
0 2000 3 5 0 0 0 330 ;
0 2000 3 6 0 0 0 450 ;
0 2000 4 7 0 0 0 380 ;
0 2000 4 8 0 0 0 290 ;
0 2000 5 9 0 0 0 340 ;
0 2000 5 10 0 0 0 380 ;
0 2000 6 11 0 0 0 280 ;
0 2000 6 12 0 0 0 450 ;
0 2000 7 13 0 0 0 330 ;
0 2000 7 14 0 0 0 450 ;
0 2000 8 15 0 0 0 380 ;
0 2000 8 16 0 0 0 290 ;
0 2000 9 17 0 0 0 340 ;
0 2000 9 18 0 0 0 380 ;
0 2000 10 19 0 0 0 280 ;
0 2000 10 20 0 0 0 450 ;
0 2000 11 21 0 0 0 330 ;
0 2000 11 22 0 0 0 450 ;
0 2000 12 23 0 0 0 380 ;
0 2000 12 24 0 0 0 290 ;
0 2001 1 25 0 0 0 340 ;
0 2001 1 26 0 0 0 380 ;
0 2001 2 27 0 0 0 280 ;
0 2001 2 28 0 0 0 450 ;
0 2001 3 29 0 0 0 330 ;
0 2001 3 30 0 0 0 450 ;
0 2001 4 1 0 0 0 380 ;
0 2001 4 2 0 0 0 290 ;
0 2001 5 3 0 0 0 340 ;
0 2001 5 4 0 0 0 380 ;
0 2001 6 5 0 0 0 280 ;
0 2001 6 6 0 0 0 450 ;
0 2001 7 7 0 0 0 330 ;
0 2001 7 8 0 0 0 450 ;
0 2001 8 9 0 0 0 380 ;
0 2001 8 10 0 0 0 290 ;
0 2001 9 11 0 0 0 340 ;
0 2001 9 12 0 0 0 380 ;
0 2001 10 13 0 0 0 280 ;
0 2001 10 14 0 0 0 450 ;
0 2001 11 15 0 0 0 330 ;
0 2001 11 16 0 0 0 450 ;
0 2001 12 17 0 0 0 380 ;
0 2001 12 18 0 0 0 290 ;
0 2002 1 19 0 0 0 340 ;
0 2002 1 20 0 0 0 380 ;
0 2002 2 21 0 0 0 280 ;
0 2002 2 22 0 0 0 450 ;
0 2002 3 23 0 0 0 330 ;
0 2002 3 24 0 0 0 450 ;
0 2002 4 25 0 0 0 380 ;
0 2002 4 26 0 0 0 290 ;
0 2002 5 27 0 0 0 340 ;
0 2002 5 28 0 0 0 380 ;
0 2002 6 29 0 0 0 280 ;
0 2002 6 30 0 0 0 450 ;
0 2002 7 31 0 0 0 330 ;
0 2002 7 32 0 0 0 450 ;
0 2002 8 33 0 0 0 380 ;
0 2002 8 34 0 0 0 290 ;
0 2002 9 35 0 0 0 340 ;
0 2002 9 36 0 0 0 380 ;
0 2002 10 37 0 0 0 280 ;
0 2002 10 38 0 0 0 450 ;
0 2002 11 39 0 0 0 330 ;
0 2002 11 40 0 0 0 450 ;
0 2002 12 41 0 0 0 380 ;
0 2002 12 42 0 0 0 290 ]
[M,ia,ic] = unique(CO2_FFD(:,2)); %find unique years, M = unique year, ia = row with unique year
m=[1;2;3;4;5;6;7;8;9;10;11;12];%set an array for 12 months
CO2_YM_averages = zeros(length(M)*12,2); %array for averages & std's, size of year*12months
for i=1:length(M)
fprintf('i = %d\n', i);
yrows = find(M(i)==CO2_FFD(:,2)); %find rows where year is equal to M(i)
for j=1:length(m)
fprintf(' j = %d\n', j);
mrows=find(CO2_FFD(yrows,3)== m(j));%find rows where month = m(i)
CO2_YM_averages(j,1) = mean(CO2_FFD(mrows,8)); %average data for each month
CO2_YM_averages(j,2) = std(CO2_FFD(mrows,8)); %std data for each month
end
end
and here is the results:
i = 1
j = 1
j = 2
j = 3
j = 4
j = 5
j = 6
j = 7
j = 8
j = 9
j = 10
j = 11
j = 12
i = 2
j = 1
j = 2
j = 3
j = 4
j = 5
j = 6
j = 7
j = 8
j = 9
j = 10
j = 11
j = 12
i = 3
j = 1
j = 2
j = 3
j = 4
j = 5
j = 6
j = 7
j = 8
j = 9
j = 10
j = 11
j = 12
Why do you say there is only one iteration for i???

3 Comments
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Jennifer Walker
Jennifer Walker on 1 Jul 2017
when I type i into the command line it returns i=1.
if you look at CO2_YM_averages where the averages and std's should be saved, it only does the first year, so I thought it was not entering the first loop a second time
Jennifer Walker
Jennifer Walker on 1 Jul 2017
Oh I see my problem now, I was rewriting over my rows by calling j in every loop. I fixed it using this:
[M,ia,ic] = unique(CO2_FFD(:,2)); %find unique years/month, M = unique year/month, ia = row with unique year/month m=[1;2;3;4;5;6;7;8;9;10;11;12];%array for 12 months CO2_YM_averages = zeros(length(M)*12,2); %array for averages, size of year/month for i=1:length(M) yrows = find(M(i)==CO2_FFD(:,2)); %find rows where year is equal to M(i) for j=1:length(m) %j=j+1; mrows=find(CO2_FFD(yrows,3)== m(j));%find rows where month = m(i) r = (i-1)*12+j; CO2_YM_averages(r,1) = mean(CO2_FFD(mrows,8)); %average data for each day CO2_YM_averages(r,2) = std(CO2_FFD(mrows,8)); end end
Jennifer Walker
Jennifer Walker on 1 Jul 2017
Thank you so much for your help! Without the print function I would have never figured it out. Thats a great trick!

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