How to show my output from matrix?

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Grace 2014-5-7

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评论： David Sanchez 2014-5-7

Hi everyone, i have

c= 1 1 1; 2 4 8; 3 9 27; 4 16 64

I extracted each row by c(1,:), c(2,:), c(3,:) and c(4,:). I want to find which row of the greatest common divisor (gcd) value with 5 is equal to 1 for each of the elements in the row vector.

ind=find(gcd(c(1,:),5)==1)

The answer gives me 1 2 3 if this command is used. I want the output is 1 as I am only interested in which row gives me all gcd value is 1.

How can i do this?

Thanks.

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Answer 1

David Sanchez 2014-5-7

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在 MATLAB Online 中打开

For all your rows:

gcd(c(k,:),5) = [1 1 1];

Then,

find(gcd(c(3,:),5)==1) = [1 2 3]

since all the elements in the first operation equal 1 (for all rows)

You want to the first element fulfilling the condition:

ind=find(gcd(c(3,:),5)==1,1)
ind =
       1

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Grace 2014-5-7

Hi David,

I wish to find which row gives me all the value is 1.

Since for all my rows: gcd(c(k,:),5)=[1 1 1];

Then the output I want to get should 1 2 3 4 because all 4 rows give me [1 1 1].

For example, if the first row and third row give me [1 1 1]. then the output should be 1 3.

The output ind shows which row gives me [1 1 1].

David Sanchez 2014-5-7

在 MATLAB Online 中打开

more clear now. The [1 2 3] you get from your commands correspond to the elements within each row and not to the rows of C, which is what you want.

You can do something like this though:

c= [1 1 1; 2 5 8; 3 9 27; 4 16 64];
N = size(c,1);
idx = zeros(N,1);
for k=1:N
    v = all(gcd(c(k,:),5) == 1); % v = 1 if all the elements of row == 1
    if v
        idx(k) = k;
    end
end