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 2016-10-05 21:50:40 +0100 received badge ● Famous Question (source) 2013-10-23 22:23:53 +0100 received badge ● Notable Question (source) 2013-05-30 05:21:21 +0100 received badge ● Popular Question (source) 2012-10-05 03:05:06 +0100 received badge ● Scholar (source) 2012-10-05 03:05:06 +0100 marked best answer Piece-wise functions and plotting It seems that this version does not ignore the x*y case: p=contour_plot(lambda x,y: F(x,y), (x,0,1), (y,0,1) ) p.show()  Lambda is not necessary: def F(x,y): if( x <= y ): return x*y return x+y contour_plot( F, (x,0,1), (y,0,1) ).show()  2012-10-05 03:04:39 +0100 commented answer Piece-wise functions and plotting Ah, thanks!... In my code, I had some nested transformations going on, so I didn't pass just the function handle. Now this works, unfortunately, it takes me back to the very poor performance which makes it impractical to put it in an @interact environment 2012-10-03 10:06:31 +0100 commented question Piece-wise functions and plotting Also, I just found out that Sage has the kronecker_delta function, so one could rewrite the above example as a product of two pieces, however, in my case I actually have three pieces and I would still need to find an appropriate transformation to map the pieces to non-overlapping conditions where the delta function would be 1 for exactly one of them. While possible, this is really not elegant. Any other thoughts? 2012-10-03 10:06:23 +0100 commented question Piece-wise functions and plotting Yes, for one-dimensional piecewise functions that would work, but for two-dimensional or more, it would not, I am afraid. 2012-10-03 09:44:10 +0100 commented answer Piece-wise functions and plotting This is a good answer in that it works, the problem now is about efficiency. If I do this with my actual function (which is a bit more complicated that the one in the example) then it takes 30 seconds to render. If I try to get fancy and make: P = lambda x,y: F(x,y); p=contour_plot( P(x,y), (x,0,1), (y,0,1) ); p.show(); Now it doesn't work again! 2012-10-02 11:25:36 +0100 received badge ● Supporter (source) 2012-10-02 11:20:42 +0100 asked a question Piece-wise functions and plotting Hi, I have a piece-wise defined function that I want to plot (and potentially do other symbolic stuff with) and I was wondering how to do this. The problem is that I am defining my function as a Python function: def F(x,y): if( x <= y ): return x*y return x+y  So I am gluing together two pieces, and I would like to be able to do (x,y) = var('x,y') contour_plot( F(x,y), (x,0,1), (y,0,1) ) But the problem is that this only plots the second part. This occurs because x <= y evaluates as false (they are variables) and F(x,y) is always evaluated as x+y. In Mathematica there is the Which function that works on symbolic expression to make piece-wise definitions. Is there an equivalent in Sage? Is there another way to do this? If I had a function (say, delta) that just evaluated as 1 if the symbolic expression was true, and 0 if not, I could craft the function as: F(x,y) = delta( x<=y ) * (x*y) + delta( x>y ) * (x+y) But as it is, I think there is no way to do this. Is there? Thanks a lot for your help, Edgar