finding values from matrix

2013 7 15
3 个回答
更新时间：2020 5 4
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Dear All
I have a matrix which is given by A= [20 140]. I want to find the location of elements in A which are greter than 45. Here is the matlab script which I tried to work upon but it gives me the whole value rather than location with respect to each coumn.
for i = 1:20
Loc(ii,:)= find(A(i,:)>45);
end
Thank you for your help

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回答（3 个）

Azzi Abdelmalek
Azzi Abdelmalek 2013-7-15
编辑：Azzi Abdelmalek 2013-7-15

2 个投票

out=A(A>45)
If you want the location:
idx=find(A>45) % corresponding indices
out=A(idx)

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Ede gerlderlands
Ede gerlderlands 2013-7-15
This gives me the total values. What I want is the position(location) of values which are greater than 45. The locationhas to be with respect to the column ex. for column 1, 5, 65 ,78 etc... for column two 4, 5,8,12,...
Azzi Abdelmalek
Azzi Abdelmalek 2013-7-15
Ok
A=randi(200,5) % Example
[ii,jj]=find(A>45)
Azzi Abdelmalek
Azzi Abdelmalek 2013-7-15
编辑：Azzi Abdelmalek 2013-7-15
A=[0 46 10 1; 47 5 48 5; 3 19 25 70]
out=arrayfun(@(x) max(find(A(x,:)>45)),1:size(A,1))

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Matt J
Matt J 2013-7-15

1 个投票

[i,j]=find(A>45);

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Ede gerlderlands
Ede gerlderlands 2013-7-15
I think am not clear with you. Is it not possible to get the location per co;umn? this gives me the over all location? isn't that? tnx
Matt J
Matt J 2013-7-15
编辑：Matt J 2013-7-15
Show us the desired output for this small example matrix
A=[0 46 10 1; 47 5 48 5; 3 19 25 70]
And explain what form the output should take (cell, matrix, structure, etc...)
Ede gerlderlands
Ede gerlderlands 2013-7-15
The answer will be 2 for the first column 1 and 3 foe the second as well as 4 for the third column. the output should be in str. Thank you
Matt J
Matt J 2013-7-15
The example matrix I gave you has 4 columns...
Ede gerlderlands
Ede gerlderlands 2013-7-15
sorry, it has to be rows
Matt J
Matt J 2013-7-15
for k=1:size(A,1)
S(k).locs = find(A(k,:)>45);
end

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Iain
Iain 2013-7-15

0 个投票

A = [45 46; 42 43];
logical_address = A>45;
A(logical_address) %gives you a single 46.
linear_index = find(logical_address);
A(linear_index) % gives you a single 46.
[rowno, colno ] = sub2ind(size(A),linear_index);
A(rowno,colno ) % gives you a single 46
Looking at your code, I think you're trying to do that row by row.
find(A(i,:)>45) will give a vector containing the column number of each column which is >45 in that row of A - the length of this may vary from row to row, so you can't store the result in a simple vector - you'd need to use a cell array.

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