MATLAB: Diff operation generating error Subscript indices must either be real positive integers or logicals

diff()MATLABsubscript error

I have a time vector which I have attached in a .mat file.

diff(time) generates the following error: Subscript indices must either be real positive integers or logicals.

time is a vector, it does not contain values to be interpreted as indices. Why is this occurring & how can I correct it?

Best Answer

You have a variable named "diff" somewhere in your workspace. MATLAB is interpreting diff(time) as an attempt to index it.

Solution: clear it or rename it to something else.

Related Solutions

MATLAB: Subscript indices must either be real positive integers or logicals.

Use the debugger. Type this at the MATLAB command prompt:

dbstop if error

Then run your code. When the error occurs, the code will pause at the offending line with all variables intact. Examine the indexing variables to see what their values are, then backtrack in your code to figure out why they are not the integers you expect them to be.

MATLAB: Second Derivative using diff

I wouldn’t use diff to calculate numerical derivatives. It has its uses, but I always use the gradient function for derivative calculations, since gradient produces a result the same size as its argument.

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MATLAB: Subscript indices must either be real positive integers or logicals.

MATLAB: Second Derivative using diff

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