How can i use roots function with a 100x3 matrix

I have a nx3 matrix. n rows and 3 columns. Every elements in a row are coefficents of a polynomial.

I want to get roots for every row.

After i get roots i want to eleminate nonlogical root and i can get logical root which i need.

Any idea of this?

Answer 1

[Guillaume]

result = cellfun(@roots, num2cell(yourmatrix, 2), 'UniformOutput', false)

Will return a nx1 cell array of column vectors which are the roots of every row.

Alternatively, do it with a loop:

result = cell(size(yourmatrix, 1), 1);
for row = 1:size(yourmatrix, 1)
    result{row} = roots(yourmatrix(row, :));
end

I have no idea what a logical or nonlogical root is.

[Gko K]

Thank you friend. That works.

This matrix is 2nd degree polynomial. So there are 2 roots. Roots can be in 2 conditions for my problem:

Condition 1:

1 negative and 1 positive

Condition 2:

2 positive(1 root is smaller, 1 roos is very bigger)

I mean with logical for Condition 1-the positive root and for Condition 2-not the bigger root.

How can i get the true root for my problem?

[Guillaume]

Then use the loop. If you only keep one root, then you don't even need a cell array:

result = zeros(size(yourmatrix, 1), 1);
for row = 1:size(yourmatrix, 1)
    rowroots = roots(yourmatrix(row, :));
    if any(rowroots < 0)
        result(row) = rowroots(rowroots >= 0);
    else
        [~, tokeep] = min(abs(rowroots));
        result(row) = rowroots(tokeep);
    end
end

[Gko K]

Thank you i will try that

[Gko K]

Thank you friend, that works :)