Evaluating function on an array of values
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Andrea Stanghellini
on 5 Apr 2021
Edited: Andrea Stanghellini
on 5 Apr 2021
I have problems with this piece of code:
f=@(x) (exp(x)-exp(-x))./(exp(1)-exp(-1))-x;
N=5;
x=linspace(0,1,N+1);
X=x(2:N);
f(X)
I would like in output an array with the evalueation of the function at each point of the vector but matlab returns me an error:
ERROR message
Array indices must be positive integers or logical values.
Error in test>@(x)(exp(x)-exp(-x))./(exp(1)-exp(-1))-x (line 1)
f=@(x) (exp(x)-exp(-x))./(exp(1)-exp(-1))-x;
Error in test (line 5)
f(X)
Where is my mistake? Do I have to install some specific package?
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Accepted Answer
Rik
on 5 Apr 2021
There are several problems here. The main one is that you are using matrix operations instead of element-wise division. In this case it doesn't matter much (as the divisor is a scalar), but it is a good habit to use ./ and .* when dealing with arrays.
The other issue is that several of the variables in your code are not defined, so we don't know what size they have. It looks like you mean X=xx(2:N) instead of X=x(2:N).
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