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Index satisfying multiple conditions

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NMans on 28 Mar 2018
Commented: NMans on 28 Mar 2018
Hi, I have a matrix with 4 columns of Year, Month, Hour, Speed. I would like to extract the data from just month 1, month 11 and month 12. My code is as below:
Wind_All = [year month day speed];
loc = find(Wind_All(:,2)==1 & Wind_All(:,2)>=11);
YEAR = [year(loc(1):max(loc))];
MONTH = [month(loc(1):max(loc))];
DAY = [day(loc(1):max(loc))];
SPEED = [speed(loc(1):max(loc))];
However, it's giving me an error message:
Index exceeds matrix dimensions. Error in Speed_Bin6 (line 34); YEAR = [year(loc(1):max(loc))];
Can someone tell me what I did wrong there? It works if it's:
loc = find(Wind_All(:,1)==2015 & Wind_All(:,2)>=11); &&indexing year 2015 and month 11 and 12.
Thank you!

Accepted Answer

Guillaume on 28 Mar 2018
I do not really understand what you are trying to do with the loc(1):max(loc) bit.
As Elias says, you want | instead of &. But note that you also did not need the find:
Wind_All = [year month day speed];
loc = Wind_All(:, 2) == 1 | Wind_All(:, 2) >= 11; %No need for find. Use logical indexing instead
filtered = Wind_All(loc, :)
And personally, I would use ismember instead of your logical expression:
Wind_All = [year month day speed];
loc = ismember(Wind_All(:, 2), [1, 11, 12]);
filtered = Wind_All(loc, :)

More Answers (1)

Elias Gule
Elias Gule on 28 Mar 2018
Just replace the '&' with '|'. Because you want the value in column 2 where the month is 1 or where the month is greater or equal to 11.

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