how to filter rows with zero values?

hello,

so i have data in mat.file 3 columns about weather conditions (first column: temperature, second column: irradiation1; third column: irradiation2 and fourth column= pv power output); i also have half the data with zero irradiation and zero output; but the temperature is not zero, so my question is how to deleted all the rows with zero irradiation; and if is there a way to only delete 90 % of these row, and keep like 10 %?

x=

0.0015 0.0044 0.0041 0.0102

0.0013 0 0 0

0.0011 0 0 0

0.0011 0 0 0

0.0010 0 0 0

0.0009 0 0 0

0.0008 0 0 0

0.0007 0 0 0

0.0006 0 0 0

0.0006 0 0 0

0.0006 0 0 0

0.0006 0 0 0

0.0006 0 0 0

0.0007 0.0005 0.0005 0.0002

0.0007 0.0061 0.0054 0.0175

Answer 1

[Rishi]

Hi Kawsar,

I understand you want to edit your file such that 90% of rows with 0 irradiation are removed.

You can use logical indexing to select the rows which have 0 irradiation. After that, you can use the 'randsample' function to select 10% of such rows. Here is the code to do so:

% Find rows where both irradiation columns are zero
rowsWithZeroIrradiation = all(x(:, 2:3) == 0, 2);

numZeroRows = sum(rowsWithZeroIrradiation);

numRowsToKeep = round(0.1 * numZeroRows);

zeroIrradiationIndices = find(rowsWithZeroIrradiation);

% Randomly select 10% of these indices to keep
indicesToKeep = randsample(zeroIrradiationIndices, numRowsToKeep);

logicalIndexToKeep = false(size(x, 1), 1);
logicalIndexToKeep(indicesToKeep) = true;

finalRowsToKeep = logicalIndexToKeep | ~rowsWithZeroIrradiation;

x = x(finalRowsToKeep, :);

You can learn more about logical indexing from the below documentation:

https://www.mathworks.com/help/matlab/math/array-indexing.html#MatrixIndexingExample-3

Hope this helps!

[Rishi]

Edited the code. 'rowsWithIrradiation' was just the negation of 'rowsWithZeroIrradiation'.

If this solved your query, please accept the answer.