MATLAB: Using if to find a value in one variable, but then give you the value of a second variable

if loop

Hi all,
Ok so I have river runoff data for around 100 days, and I would lke to find the time of maximum runoff on each day. I reshaped the data (Q) into an x,y matrix (hours,days), but so far have had no luck getting the code to work. I tried it first with made up data and the code below worked fine:
for x=1:24;
for y=1:4;
if Q(x,:)==max(y)
Peak=T(x,:);
end
end
end
The variable T is matrix of the time with 1:24 repeated for each day. Peak is the variable of time of maximum runoff.Trouble is I can't get this to work with my real data, I have already taken out the NaNs and replaced them with 1. There is no error it just runs through without making Peak. I found the maximum for each day sepeately and it works fine for days without NaNs. Any ideas??
I would be greatful for any suggestions, Thanks, Cat

Best Answer

[val,idx] = max(Q)
This is the row-wise maximum, i.e. along the rows for each column. idx says on which row the max is found. Since each day is a different column, the idx tells you which hour.
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