How do I display only positive numbers from a matrix, i.e column 1 has to be positive to display the corresponding 3 columns of data?

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Christopher Wolfe 2021-9-12

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评论： Walter Roberson 2021-9-12

I have column 1 which shows the index returns for each day, the next 3 columns are stock price returns from the corresponding day. There are currently days displaying a negative return for the index and the 3 stock prices next to it. I want to code that I only want to display the positive index returns and the corresponding stock prices of that same day.

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Christopher Wolfe 2021-9-12

The returns are denoted in this line rets = log(price(2:end,:)./price(1:end-1,:));

Ive J 2021-9-12

在 MATLAB Online 中打开

A = [randi([-10 10], 4, 1), randi([20 100], 4, 3)]
A = 4×4
     3    20    63    45
    -6    20    45    45
    -6    33    54    80
    10    99    48    61
idx = A(:, 1)  > 0; % positive indices only
newA = A(idx, :)
newA = 2×4
     3    20    63    45
    10    99    48    61

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回答（1 个）

Walter Roberson 2021-9-12

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在 MATLAB Online 中打开

mask = find(rets >= 0);
prets = rets(mask);
pprice = price(mask+1,:);

rets(K) is calculated based upon both price(K+1,:) and price(K,:) so it is not clear which of the two days you would want to have displayed. Here I chose to have it associated with the second day rather than the first.