# Question:Random Float(undefined)'s or me being dense

## Question:Random Float(undefined)'s or me being dense

Maple

Hey i am trying to get maple to do some differential equation solving and i am running into some major road blocks.

the code i am using is as follows: restart;

M[Star] := 2*10^30;

M[planet] := 2*10^27;

q := M[planet]/M[Star];

g := sqrt((R-a)^2);

H := 0.333e-1*R;

Delta[p] := H;

Alpha := unapply(piecewise(R < a, -6.67*q^2*10^(-11)*M[Star]*(R/Delta[p])^4/(2*R), R > a, 6.67*q^2*10^(-11)*M[Star]*(a/Delta[p])^4/(2*R), R = a, 1), R, a);

PDE1 := diff(S(R, t), t) = 3*(diff(R^(1/2)*(diff(S(R, t)*R^(1/2)-2*Alpha(R, a)*S(R, t)^(3/2)/(6.67*10^(-11)*M[Star])^(1/2), R)), R))/R:

Alpha(R,a);

f(R):=((e)^(-((R-1)^(2))/(2(0.01)^(2))))/(0.01(2 Pi)^(1/(2)));

a:=0.5;

IBC := {S(99, t) = 0, S(0.1e-1, t) = 0, S(R, 0) = f(R)};

eval(PDE1);

PDE2 := subs(Float(undefined) = 0, eval(PDE1));

pds1 := pdsolve(PDE2, IBC, numeric, S(R, t), time = t, range = 0.1e-1 .. 99, spacestep = 0.1e-1, timestep = 0.25e-4);

p0 := pds1:-plot(S, t = 0, R = 0.1e-1 .. 99, color = pink);

p1 := pds1:-plot(S, t = 0.1667e-3, R = 0.1e-1 .. 99, color = green);

p2 := pds1:-plot(S, t = 0.6667e-3, R = 0.1e-1 .. 99, color = blue);

p3 := pds1:-plot(S, t = 0.2667e-1, R = 0.1e-1 .. 99, color = red);

p4 := pds1:-plot(S, t = 0.10667e-1, R = 0.1e-1 .. 99, color = orange);

p5 := pds1:-plot(S, t = 0.42667e-1, R = 0.1e-1 .. 99, color = brown);

plots[display]({p0, p1, p2, p3, p4, p5})

running this goes through all the way till the end until the bit where i get maple to process the equation for the graphs at which point i get the following error,

"Error, (in pdsolve/numeric/plot) unable to compute solution for t<0.:
unable to store (Float(undefined)+Float(undefined)*I)*(Float(undefined)+Float(undefined)*I+Float(undefined)*2000000000000000000000000000000^(1/2)) when datatype=float"

This is what i find quite odd, i'm unsure where all the "Float(undefined)'s are coming from unless i'm just being really dense.

if any one has any ideas i would be greatly appreciative.

Many thanks,

Josh Barker  ﻿