jaytreiman

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14 years, 317 days

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I was playing with plots:-fieldplot in Maple 2019 and found that sometime the grid option gives a strange result.  The code I used was

with(plots):
fieldplot([-x/(x^2+y^2)^1.5,-y/(x^2+y^2)^1.5],x=-1..1,y=-1..1);
fieldplot([-x/(x^2+y^2)^1.5,-y/(x^2+y^2)^1.5],x=-1..1,y=-1..1,grid=[8,8]);
fieldplot([-x/(x^2+y^2)^1.5,-y/(x^2+y^2)^1.5],x=-1..1,y=-1..1,grid=[7,7]);

The first two plots come out as expected.  The third plot has (0,0) in the grid, a point where the vector field does not exist.  Rather than giving an error or ignoring the point, Maple 2019 (and 2018) plots a single arrow through the origin. The file with plots is below.  I hope that this can be changed to give a different output.

 


 

with(plots):
fieldplot([-x/(x^2+y^2)^1.5,-y/(x^2+y^2)^1.5],x=-1..1,y=-1..1);
fieldplot([-x/(x^2+y^2)^1.5,-y/(x^2+y^2)^1.5],x=-1..1,y=-1..1,grid=[8,8]);
fieldplot([-x/(x^2+y^2)^1.5,-y/(x^2+y^2)^1.5],x=-1..1,y=-1..1,grid=[7,7]);

 

 

 

 


 

Download fieldplots_1.mw

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I was writing problems about the bisection method and decided to use the Maple routine Student[NumericalAnalysis][Bisection].  The problem I wrote generates a cubic with all three roots in a somewhat random interval.  Students are then asked to find a root to a given accuracy using the bisection method.  If one does not hit a root, the Student[NumericalAnalysis][Bisection] routine gives the desired answer.

A problem arises when the bisection algorithm...

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