awass

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18 years, 302 days

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These are questions asked by awass

Hi,

I am using Maple 2023 on a Mac. When I issue the following commands

with(plots);
for j to 10 do
    pl || j := plot(sin(j*x)^j, x = 0 .. 5);
end do;
display([pl || (1 .. 10)], insequence = true);

I used to get an animation but also some controls: I could easily repeat, reverse, change FPS, etc. Now I seem to have to go Format_>Plot->Animate->Play. Has there been a change in Maple or have set some preference to this awkward form? I admit I have not been using Maple a lot these last couple of years.

S := [1, 2];
                          S := [1, 2]

T := [1, 2];
                          T := [1, 2]

is(S = T);
                              true

Sv := Vector([1, 2]);
                              

Tv := Vector([1, 2]);
                              

is(Sv = Tv);
                             false

is(convert(Sv, list) = convert(Tv, list));
                              true

I have a document with quite a few symbols saved to my favorites palette. When I close the file and then reopoen it the Favorites Palette has not changed-the symbols are right where I want them. However, if I open the file with another computer the Favorites Palette is empty! What is happening?  (The document is stored in Dropbox and both computers are Macs running Maple 2023.)

I  had to deal with a long number x =  521...773 that i wanted to break up into 3 digit segments. I converted x to a string and got y="521...773". Then I used String Tools to LengthSplit y and got a sequence z="521", ..."773". So far so good. Next I tried to extract the 3 digit segments and tried
convert(z[1],integer) but that led to

Error, (in anonymous procedure called from depends) too many levels of recursion

Very mysterious. The command convert("521",name)  gave me the symbol 521, not the number.
I eventually stumbled across parse("521") and that gave me what I wanted,namely the integer 521. I looked at the Help page for parse but decided I did not want to delve into that bit of arcane knowledge.

I also tried several times to write little procedures to strip off the double quotes but was unsuccessful.

I am sure there is a more obvious way to go about this. Any suggestions?

restart;
Here is my pde and a procedure that plots the solution.
K1:=proc(g)
uses PDEtools,plots:
local pde, ic,ans;
pde:=-4*x*diff(f(u,x),u,x)+4*diff(f(u,x),u)=x^4*diff(f(u,x),x,x)+x^3*diff(f(u,x),x)+8*x^2*f(u,x)*(1-f(u,x)^2);
ic:={f(u,0) = 1, f(u,1) = 0,f(0,x)=g};
ans:=pdsolve(pde,ic,numeric,compile=true,time=u,range=0..1,'spacestep'=0.005);
ans:-plot(u=3)
end proc:
K1(1+x^2-2*x^3);

It works just fine; I get a plot of f(u,x) for u =3.  (Note that unlike dsolve there is no complaint about the global variable g in the initial conditions.)
Now I want to see a plot of diff(f(u,x) for u=3.
K2:=proc(g)
uses PDEtools,plots:
local pde, ic,ans;
pde:=-4*x*diff(f(u,x),u,x)+4*diff(f(u,x),u)=x^4*diff(f(u,x),x,x)+x^3*diff(f(u,x),x)+8*x^2*f(u,x)*(1-f(u,x)^2);
ic:={f(u,0) = 1, f(u,1) = 0,f(0,x)=g};
ans:=pdsolve(pde,ic,numeric,compile=true,time=u,range=0..1,'spacestep'=0.005);
ans:-plot([diff(f(u,x),x,u),color=cyan],u=3)
end proc:
K2(1+x^2-2*x^3);

That does not work.

I try to introduce a new variable h(u,x) = diff(f(u,x),x) so that I can plot h(u,x).
K3:=proc(g)
uses PDEtools,plots:
local pde, ic,ans;
pde:={h(u,x)=diff(f(u,x),x),
-4*x*diff(h(u,x),u)+4*diff(f(u,x),u)=x^4*diff(h(u,x),x)+x^3*h(u,x)+8*x^2*f(u,x)*(1-f(u,x)^2)};
ic:={f(u,0) = 1,f(u,1) = 0,f(0,x)=g};
ans:=pdsolve(pde,ic,numeric,compile=true,time=u,range=0..1,'spacestep'=0.005);
ans:-plot(h(u,x),u=3)
end proc:

K3(1-x^2);
Error, (in pdsolve/numeric/par_hyp) Incorrect number of initial conditions, expected 2, got 1

I have no idea what Maple is referring to; there are 3 initial conditions, not 1 or 2.

Anybody know what is going on? Any idea how to get what I need?

One more comment. I have never knowingly used a module in all the years I have been using and teaching Maple. I am sure there are good reasons for the construct but I think it would be difficult to teach. For ode's the result of dsolve is a procedure and it is relatively easy to teach because procedures are the bread and butter of using Maple. Why does pdsolve return a module?  I spent a good deal of time figuring out the use of pdsolve and would not like to force my students to do the same. I get them up to speed solving ode's using dsolve and DETools in a one hour lab. I wonder how much time it would take to do pdsolve.

 

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