As signal was defined with signal=readtable(... I bet signal is a table, I think you want to pass in one of the listed types to fft. What's in signal?
class(signal) % will tell you what class the variable is, I think it's a table
Is it a table with one variable? Is the variable called Var1
head(signal) % wlil show you the top few rows of the table, I think it's a single Variable called Var1
Assuming table is a variable called Var1, and that the variable contains numeric data (i.e. one of the listed types in the error message you received), consider
x = fft(signal.Var1, n);
But of course if it's a different variable you'll need to use that name, and if it's not numeric you'll have to convert it one way or another.
Also I'm a little wary of your use of pwelch on the fft result, are you sure that's what you wanted?
