How to Add Multiple Arrays?
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I am new to matlab. I want to do the following: I had created nine arrays and gave each one a name from A to I, said: A,B,C,D,E,F,G,H,I. Once I done that what I want to do is add them in groups of three and put to each new array the name of the last array added. For example. array C=A+B+C, array F=D+E+F, array I=G+H+I, I want to do this using a for loop which I think will be the most practical way of do it.
Thank you
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Oleg Komarov
le 19 Mar 2011
If you could know how many matrices you have in advance (num), then preallocate before the loop:
dir1='C:\Documents and Settings\ann\My Documents\MATLAB\AMSR-E';
A = zeros(586,1383,num);
c = 1;
for year=2010:2010
for month=10:12
for day=1:eomday(year,month)
dd = [num2str(year),'.',num2str(month,'%0.2d'),...
'.',num2str(day,'%0.2d')];
file1 = ls([dir1,'\',dd,'\*.hdf']);
A(:,:,c) = hdfread([dir1,'\',dd,'\',file1],...
'Ascending_Land_Grid',...
'Fields', 'A_Veg_Water_Content');
% Increase counter
c = c+1;
end
end
end
You'll end up with a 3d array.
EDIT
Then to consolidate as Sean suggested use sum(A,3) in a loop:
A = rand(586,1383,8);
% Number of days to consolidate each time
n = 3;
% Final amount of slices
sl = ceil(size(A,3)/n);
% Preallocate
B = zeros(586,1383,sl);
for s = 1:sl-1
B(:,:,s) = sum(A(:,:, (s-1)*n+1:s*n ), 3);
end
% Final slice can be the result of less than 3 days
B(:,:,s+1) = sum(A(:,:,s*n+1:end),3);
Oleg
3 commentaires
Oleg Komarov
le 19 Mar 2011
If you have NaNs then you should consider how to treat them, otherways they'll propagate causing loss of info.
Plus de réponses (2)
Andrew Newell
le 19 Mar 2011
It's not clear to me why you want loops. As long as the arrays are the same size, you can just enter the equations the way you wrote them above, e.g.,
C = A+B+C
and it will work.
9 commentaires
Sean de Wolski
le 19 Mar 2011
doc cat
doc sum
2 commentaires
Matt Tearle
le 19 Mar 2011
When you say "alternatively", do you mean "columns rather than rows" or "alternating columns"?
Former: sum(A,2)
Latter: sum(A(:,1:2:end))
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