MATLAB: Index must be a positive integer or logical

maximum

For the following operation in my code:

    result = max((1)-(abs(sum_A-sum_B)/sum_A-sum_C),0);

I got the following error:

Attempted to access max(356.87,0); index must be a positive integer or
logical.

Although I'm intending to simply retrieve the maximum value here, provided that when I run the line as stand-alone, I get the max retrieved correctly.

What could be the issue?

Thanks.

Best Answer

Are you using max as a variable somewhere in your code? If not, it's probably in your workspace, so do a

 clear max

and re-run your code. At any rate, try to avoid variable names that are also function names or reserved words.

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MATLAB: Getting error when asking from max and min for negative values.

Sounds like you may be trying to index into the array using the min or max value instead of the index:

mn = min(data);
minValue = data(mn);

Don't do that. Use both values if you want to get the index. A better way:

[minValue, indexOfMin] = min(data);
[maxValue, indexOfMax] = max(data);

Or you may have used min for the variable

min = min(data);  % Horrible idea

in which case when you came along and tried to do it again, it would have used your min array (a vector is data was a 2-D array) as indexes into your newly created min array. min() is no longer the min function if you replaced it with a variable of the same name. So if the min was now an array of column mins because you stored the mins in an array called min, then doing min(data) will throw that error if any elements of data have negative, zero, or floating points (fractional) values.

MATLAB: Changing time from decimal days to +- 0 from high water

Guessing a bit, because you don't tell us what pf and tf are, but assuming they are water height and time vectors, I suspect that it may help to change the first line of code to

[~, pkindex] = max(pf);

This is because the first result from max (in this case 1.8268) is the maximum value stored in the vector pf. What you need is not, I think, that value, but the index at which it is stored, which is the second result from max.

Best Answer

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MATLAB: Getting error when asking from max and min for negative values.

MATLAB: Changing time from decimal days to +- 0 from high water

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