finding location of numbers in matrix

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sisay
sisay il 17 Lug 2013
I have a matrix of A= 65 x 500. I want to find the position (location) of data in 'A' which are above 300. It really giving me trobles can somebody help me with this?
I tried this but with no avail. Btw. the number of datapoints which are above 300 varies among rows.
for jj= 1:size(A,1)
[ i j]= find(A>300);
end
And this gives only the total number of data points. Not row wise. Any help

Risposte (4)

Andrei Bobrov
Andrei Bobrov il 17 Lug 2013
A=[2 3 4; 3 2 2 ;5 6 7]
[ii,jj]=find(A'>2)
out = accumarray(jj,ii,[],@(x){x'})

the cyclist
the cyclist il 17 Lug 2013
Modificato: the cyclist il 17 Lug 2013
Just this one line gives all the (i,j) coordinates, for all rows.
[i j]= find(A>300);
So, if you are interested in row 7 (for example), then find where i=7, and look at the corresponding values of j.
If you absolutely must do it separately for each row (for reasons you do not explain here), then you could do
for ii= 1:size(A,1)
j{ii} = find(A(ii,:)>300);
end
The ii th element of the cell array will have the indices for row ii.
  2 Commenti
Ede gerlderlands
Ede gerlderlands il 17 Lug 2013
Modificato: Ede gerlderlands il 17 Lug 2013
To put it simpler . If I have A=[2 3 4; 3 2 2 ;5 6 7] and If I want the location of points for A>2 for each row. What I expect is for each row is something like this
2 3
1
1 2 3
Ede gerlderlands
Ede gerlderlands il 17 Lug 2013
Thank you I have got it...

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Azzi Abdelmalek
Azzi Abdelmalek il 17 Lug 2013
[ii,jj]=find(A>300)
  2 Commenti
Ede gerlderlands
Ede gerlderlands il 17 Lug 2013
Modificato: Ede gerlderlands il 17 Lug 2013
Thank you .This gives the position of total number of data points which are greater than 300. Not the position within each row.
Azzi Abdelmalek
Azzi Abdelmalek il 17 Lug 2013
for k=1:size(A,1)
idx{k}=find(A(k,:)>300)
end

Accedi per commentare.


Azzi Abdelmalek
Azzi Abdelmalek il 17 Lug 2013
id=arrayfun(@(x) find(A(x,:)>300),(1:size(A,1))','un',0)

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