Piecewise function in octave

[Ben Abbott]

".*" is element by element multiplication, where "*" is matrix  
multiplication.

	f = @(t) a(t) .* (t<t0) + b(t) .* (t==t0) + c(t) .* (t>t0);

For example,

	octave-3.1.51+:1> a = @(t) -1;
	octave-3.1.51+:2> b = @(t) 0;
	octave-3.1.51+:3> c = @(t) 1;
	octave-3.1.51+:4> f = @(t,t0) a(t) .* (t<t0) + b(t) .* (t==t0) +  
c(t) .* (t>t0);
	octave-3.1.51+:5> t = (-10):10;
	octave-3.1.51+:6> x = f(t,0);
	octave-3.1.51+:7> x
	x =
	  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1   0   1   1   1   1   1    
1   1   1   1   1
	octave-3.1.51+:8> x = f(t,3)
	x =
	  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1  -1   0   1   1    
1   1   1   1   1

Ben


On Oct 15, 2008, at 5:42 PM, genehacker wrote:

>
> Hi Carlo,
>
>    Can you please tell what .* do to the equation. Also how would  
> you write
> a generalised piecewise function like
>
> f(t) =  a(t) t < t0
>         b(t) t = t0
>         c(t) t > t0
>
> thanks in advance,
> k3.
>
>
> Carlo de Falco-2 wrote:
>>
>>
>> On 15/ott/08, at 21:57, genehacker wrote:
>>
>>> Hi,
>>>
>>>  I am looking for a code that can specify a function f(t)
>>> piecewise, i.e.
>>> that can be defined according to intervals based on value of t. I
>>> want to
>>> integrate one of these in an anonymous function g(x,t).
>>>
>>> f(t) = sin(t)  t<pi
>>>      0         t>=pi
>>>
>>> cheers
>>> k3
>>
>> to implement the example above you could use
>>
>> f = @(t) sin(t) .* (t<pi) ;
>>
>> c.
>>
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>
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