How to delete multiple rows from a table using a for loop (with a condition)?

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I would like to delete multiple rows form a table (imported from Excel).
I have "n" number of rows with 5 columns (Var1,..........,Var5). Now if in column 5 (Var5), there is value greater than 0, I want that row and the next three rows to be deleted.

Accepted Answer

Jeremy Hughes
Jeremy Hughes on 2 Sep 2021
I wouldn't use a for loop. MATLAB excells at array operations.
A = randn(12,5); % Make some data with positive and negative values
A(1:4:5) = -abs(A(1:4:5));
A(end-4:end) = -abs(A(end-4:end));
T = array2table(A)
T = 12×5 table
A1 A2 A3 A4 A5 _________ ________ ________ ________ ________ -0.18657 0.76498 0.23522 -0.86791 0.35787 0.74813 0.73723 -0.13228 0.05872 -1.1772 1.4034 -1.6129 -0.55285 2.2033 0.20268 0.91163 0.915 -1.3487 -0.31358 0.16887 -1.3759 1.4728 0.98564 -1.0473 0.34148 -0.68973 -0.28485 -0.98694 0.29496 1.4129 2.4566 -0.9063 -1.3356 -1.1073 2.1731 -0.068694 -0.3263 0.90646 -0.19821 -1.1389 1.1861 1.0306 3.1811 -2.0224 -0.60713 -0.044051 -0.62426 0.72973 -0.58808 -0.66111 0.46205 0.12273 1.0989 0.013466 -1.363 -0.63828 0.81857 -0.54734 0.59388 -0.76208
rowIdx = find(T.A5 > 0);
rowIdx = rowIdx(:) + (0:3); % expands column + row
T(rowIdx,:) = [] % deletion
T = 2×5 table
A1 A2 A3 A4 A5 ________ _______ ________ ________ ________ 0.46205 0.12273 1.0989 0.013466 -1.363 -0.63828 0.81857 -0.54734 0.59388 -0.76208
You can also only check every fourth row, but there's some tricky math.
rowIdx = find(T.A5(1:4:end) > 0) % check every 4th entry will result in the "block" index though
rowIdx = 4*(rowIdx-1)+1; % re-align to the right places in the original array
rowIdx = rowIdx(:) + (0:3); % expands column + row
T(rowIdx,:) = [] % deletion
T = 2×5 table
A1 A2 A3 A4 A5 ________ _______ ________ ________ ________ 0.46205 0.12273 1.0989 0.013466 -1.363 -0.63828 0.81857 -0.54734 0.59388 -0.76208

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