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From: Shaun on 19 Feb 2010 11:48
I am wanting to plot a piecewise continuous function, I am not able to find the correct syntax to do this. Here is a simple example that should give a triangle centered at x=0,

f(x)= { 1+x -1<=x<=0
{ 1-x 0<x<=1

This is how I am incorrectly trying to do this (it seems others suggest this approach over using the inline function)

x=-1:0.01:1;
f = @(x) ( (1+x).*(-1<=x<=0) + (1-x).*(0<x<=1) );
plot(x,f(x))

How can I fix this or is there a better approach?
From: James Allison on 19 Feb 2010 12:05
Very close. This works:

f = @(x) ((1+x).*(and(-1<=x,x<=0)) + (1-x).*(and(0<x,x<=1)))
fplot(f,[-1 1 0 1])

Note that f is undefined outside the interval [-1 1].

-James

Shaun wrote:
> I am wanting to plot a piecewise continuous function, I am not able to
> find the correct syntax to do this. Here is a simple example that
> should give a triangle centered at x=0,
>
> f(x)= { 1+x -1<=x<=0
> { 1-x 0<x<=1
>
> This is how I am incorrectly trying to do this (it seems others suggest
> this approach over using the inline function)
>
> x=-1:0.01:1; f = @(x) ( (1+x).*(-1<=x<=0) + (1-x).*(0<x<=1) );
> plot(x,f(x))
>
> How can I fix this or is there a better approach?
From: Shaun on 19 Feb 2010 12:46
Thanks for the response.

Is there any way to plot this using plot(x,f)? What I want to do is plot different piecewise continuous functions along with their approximations. So, how can I get the function f in the correct form for the plot command? Then I could compare the exact function f and the approximate function f_appx on the same plot: plot(x,f,x,f_appx).
From: James Allison on 19 Feb 2010 12:59
Sure:

f = @(x) ((1+x).*(and(-1<=x,x<=0)) + (1-x).*(and(0<x,x<=1)));
x=-1:0.01:1;
plot(x,f(x))

-James

Shaun wrote:
> Thanks for the response.
>
> Is there any way to plot this using plot(x,f)? What I want to do is
> plot different piecewise continuous functions along with their
> approximations. So, how can I get the function f in the correct form
> for the plot command? Then I could compare the exact function f and the
> approximate function f_appx on the same plot: plot(x,f,x,f_appx).
From: Shaun on 19 Feb 2010 13:32
That works, I thought I already tried that, but I guess not. Thanks again for the quick help.
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