How can I create a piecewise inline function in MATLAB?

Question

I have a function in MATLAB which takes another function as an argument. I would like to somehow define a piecewise inline function that can be passed in. Is this somehow possible in MATLAB?

Edit: The function I would like to represent is:

f(x) = { 1.0,  0.0 <= x <= 0.5,
         -1.0, 0.5 < x <= 1.0

where 0.0 <= x <= 1.0

Solution 1

Unfortunately, MATLAB doesn't have a ternary operator which would make this sort of thing easier, but to expand slightly on gnovice's approach, you could create an anonymous function like so:

fh = @(x) ( 2 .* ( x <= 0.5 ) - 1 )

In general, anonymous functions are more powerful than inline function objects, and allow you to create closures etc.

Solution 2

If you really want to make an inline function (as opposed to an anonymous function), then the following would probably be the simplest way:

f = inline('2.*(x <= 0.5)-1');

However, as pointed out in the other answers, anonymous functions are more commonly used and are more efficient:

f = @(x) (2.*(x <= 0.5)-1);

Solution 3

I just had to solve that problem, and I think the easiest thing to do is use anonymous functions. Say that you have a piecewise function:

when x<0    : x^2 + 3x
when 0<=x<=4: e^x
when x>4    : log(x)

I'd first define logical masks for each piecewise region:

PIECE1 = @(x) x<0
PIECE2 = @(x) x>=0 & x<=4
PIECE3 = @(x) x>4

Then I'd put them all together:

f = @(x) PIECE1(x).*(x.^2+3*x) + PIECE2(x).*exp(x) + PIECE3(x).*log(x)

x = -10:.1:10
figure;
plot(x,f(x))