Function with Non Constant Variable

Hello,

I'm wondering if there's a way to run this code while keeping x a variable (Instead of inputting a number for the required input 'x', have a variable so I can create a graph of results). Currently I just recieve output 'Unrecognized Function or variable 'x', even when putting sym x in the code.

Thanks for any help!

[Adam Danz]

Please provide example inputs.

[User7605]

It runs fine when all 4 inputs are numbers, [eg. (3, 2, 1, 1)] but I want the x input to work as a variable [(eg y)]. Hope that makes sense

[per isakson]

x must have a value, e.g.

%%
x = 17;
S(3,1,x,2)

or maybe the Symbolic Toolbox lets you use a variable, x, without a value.

[Adam Danz]

" I want the x input to work as a variable"

This part is still unclear, hence the variety of answers. Do you mean you want to pass a variable to the 3rd input (see per isakson's or Stephen Cobeldick's answer) or do you mean that the 3rd variable should be a symbolic variable (see Walter Roberson's answers).

Answer 1

[Stephen23]

You could create an anonymous function:

fun = @(x) S(3,1,x,2);
..
fun(17)

Answer 2

[Walter Roberson]

syms x
output = S(3, 1, x, 2);
disp(output)
output = S(3, 1, 4, 2);
disp(output)

function SF = S(F, a, x, n)
if isa(a, 'sym') || isa(x, 'sym')
SF = piecewise(x >= a, F*(x-a)^n, 0);
elseif x >= a
SF = F.*(x-a).^n;
else
SF = zeros(size(x));
end
end

[Walter Roberson]

[Please preserve the above for investigation of a system problem.]

Answer 3

[Walter Roberson]

syms x
output = S(3, 1, x, 2);
disp(output)

{3 (x−1)20 if  1≤x otherwise

output = S(3, 1, 4, 2);
disp(output)

    27

function SF = S(F, a, x, n)
if isa(a, 'sym') || isa(x, 'sym')
SF = piecewise(x >= a, F*(x-a)^n, 0);
elseif x >= a
SF = F.*(x-a).^n;
else
SF = zeros(size(x));
end
end