Evaluating function on an array of values

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?

Answer 1

[Rik]

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).

[Andrea Stanghellini]

Thanks,

I have edited my question and I'm sorry for the initial code description. I have made also the corrrection in the definition of the function substituting / with the operator ./ but the program does not work

[Rik]

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)

ans = 1×4

-0.0287 -0.0505 -0.0583 -0.0443

Did you create a variable with the name exp?

[Andrea Stanghellini]

No I didn't but I solve the problem, thank you so much.