Calculating value of function in point

I have to write Matlab function:function value = evaluate(f,x,y,n) that evaluates value of real function f on equidistant array of n points on segment [x,y]. Function has to return vector of dimension 2xn, such that in first row are points from equidistant array, and in second row is function value in those points.

Here is my try, but this code doesn't seem to work. I get errors when I run this code. Any help is appreciated.

f=@(x)2*x+2^x;
test = evaluate(f,0,6,7);
function value = evaluate(f,x,y,n)
a = linspace(x,y,n);
b = f(a(1:n));
matrix = [a:b];
end

Answer 1

[Matt J]

f=@(x)2*x+2.^x;
test = evaluate(f,0,6,7)

test = 2×7

0 1 2 3 4 5 6 1 4 8 14 24 42 76

function matrix = evaluate(f,x,y,n)
a = linspace(x,y,n);
b = f(a);
matrix = [a;b];
end

[Ds31]

So what was mistake in my code?

[Matt J]

1. 2.^x instead of 2^x
2. [a;b] instead of [a:b]
3. The return argument needs to be "matrix" instead of "value"