# How to plot a triangular shape function on a triangular domain?

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Soroush Asarzadeh on 25 Apr 2016
Commented: Soroush Asarzadeh on 27 Apr 2016
Hello, I want to plot the following shape function: N(s,t)=t*(2*t-1) It has to look like the following diagramm:
but I get this one:
Here is my code:
[s,t]=meshgrid(0:0.1:1,0:0.1:1)
N3=@(s,t)t.*(2*t-1);
surf(s,t,N3(s,t))
I know that the problem is with the rectangular domain, that meshgrid generates. But I don't know how to define a triangular domain. Has anybody an idea?
Thanks

Mike Garrity on 25 Apr 2016
I described one approach in this thread.
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Mike Garrity on 26 Apr 2016
I think that passing a function handle into surf is making things more complicated than you really need.
I don't know what N3 is, but using the N from the top, I get this:
[s,t] = meshgrid(0:0.025:1);
z = t.*(2*t-1);
z(s+t > 1) = nan;
surf(s,t,z)
Soroush Asarzadeh on 27 Apr 2016
Thank you very much Mike!