How to declare a function having bounds ?

example-

    f(x)= 0 x<0

        x 0<x<1

       -1 x>1

[David Young]

What is supposed to happen if x=0 or x=1? I'm guessing you mean

0 if x < 0
x if 0 <= x <= 1
-1 if x > 1

[David Webb]

function given above is just for example not the actual function. Just wanted to know how to declare such a function.

Answer 1

[Matt J]

One way,

f=@(x) x.*(x>=0 & x<=1) - (x>1)

[David Webb]

Can you please explain ... Thanks!!

[David Webb]

Got it Thanks man !!

Answer 2

[David Young]

I would go for a vectorised function:

function x = clipZeroOne(x)
x(x < 0) = 0;
x(x > 1) = -1;
end

Test examples

clipZeroOne(9)
clipZeroOne(0.5)
clipZeroOne(-0.5)
clipZeroOne([-Inf -3 0 0.2 0.9 1 15 Inf])    % apply to a vector

Answer 3

[Erik S.]

function f=fcn(x)
 if x<0  
  y = 0;  
 else if x>=0 && x<1  
  y = x;  
 else if x>1
  y = -1;
 end

In the example f(0) = x.

[David Webb]

Thanks for the answer ..

[David Young]

This answer has multiple issues, as they like to say on Wikipedia.

• What happens if x is exactly equal to 1?
• The output variable is f but you assign the result to y.
• "else if" isn't legal MATLAB.
• The "{} Code" button makes the code display clearly.

I guess what you meant was this

function y = fcn(x)
if x<0
  y = 0;
elseif x<1   % it must be greater than or equal to 0
  y = x;
else
  y = -1;    % it must be greater than or equal to 1
end
end