how to combine symbolics and if statement?

Hello, My function is like this

 y=x+2 for 0<=x<=10 
 y = x^2 for 10<x<=500 and x belongs to 0,500.

so I tried like this

syms x
if x>=0 && x<=10
    y=x+2
else y=x^2
end

but i am getting an error saying

"Conversion to logical from sym is not possible" 
"Operands to the || and && operators must be convertible to logical scalar values".

Please help me how to overcome this.

Answer 1

[Walter Roberson]

You cannot use if together with symbolic expressions.

You should be considering using numeric expressions together with logical indexing. See though http://www.mathworks.com/matlabcentral/answers/301165-ode-suite-for-solving-switched-systems#comment_397941 for a discussion on hidden problems with one way of coding that.

You could also code the obscure

evalin(symengine, 'piecewise([0 <= x and x <= 10, x+2], [10 < x and x <= 500, x^2])')

but you will find that it probably will not be of any use to you.

[Karthik Nimishakavi]

thanks, I'll try that

Answer 2

[Karan Gill]

Piecewise is available starting 16b: <http://www.mathworks.com/help/symbolic/piecewise.html>

In this case:

syms y(x)
y(x) = piecewise(0<=x<=10, x+2, 10<x<=500, x^2);

Now try

y(1)
ans =
  3

>> y(12)
ans =
  144

[Walter Roberson]

Thanks, Karan, I had missed seeing that.