how to solve tis type of pdefirst_order_pde.mw

I obtained a Plot p, then trying to find if it has Float(undefined) in it. I am basically trying to find if DEplot returns an empty plot or not. I found that it the plot structure has HFlat(undefined) then this seems to imply an empty plot. So I said, then in the code I can check for HFlat(undefined) in the plot and it is there, then I know the plot is empty.

But this check is not working.

I used has(....,Float(undefined)) and this returns false. But if I copy and paste part of the plot structure and try the check on the copy, it gives true. 

I do not understand what is the difference. First here is screen shot, and below if complete code to reproduce.

restart;
ode2:=2*y(t)+t*diff(y(t),t) = t^2-t+1;

p:=DEtools:-DEplot(ode2,y(t),t=0..3.5,y=0..3,
                        linecolor = red,                        
                        arrowsize ='magnitude',
                        numpoints = 200 ,
                        axes = boxed,color = ('magnitude[legacy]')):


p0:=Array(1 .. 3,1 .. 2,{(1, 1) = HFloat(undefined), (1, 2) = HFloat(undefined), (2
, 1) = HFloat(undefined), (2, 2) = HFloat(undefined), (3, 1) = HFloat(undefined
), (3, 2) = HFloat(undefined)},datatype = float[8],order = C_order);
whattype(p0);
has(p0,HFloat(undefined)) 

p1:=op([1,2],p);
whattype(p1);
has(p1,HFloat(undefined)) 

Worksheet attached also.

Maple 2023.2 on windows 10
 

question is: Why the above give different result? And what is the correct way to check if the output plot from DEplot is empty or not (in code)?

Download why_has_works_different.mw

The documentation says:

So “_” can be treated as an argument placeholder in a for–in loop. Nevertheless, I would like to know if there is an argument placeholder like MatLab's tilde (~) operator:

• Ignore Function Outputs
• Ignore Inputs in Function Definitions

Ordinarily, there is no need to to ignore inputs in function definitions, but as for the former, since there is a _nresults keyword in Maple (and some "built-in" routines do use it), when accessing the source code is unavailable, how do I ignore specific outputs from such a function (e.g., a procedure with option encrypted that has been loaded from a repository)?
For instance, the help page of MTM:-eig mentions three calling forms: 

1. l := MTM:-eig(A): 
2. [V,L] := MTM:-eig(A): 
3. [V,L,N] := MTM:-eig(A): 

If I do not directly invoke the linalg/Student[LinearAlgebra]/LinearAlgebra/Matlab package (and do not manually compute Eigenvals), will it be possible to imitate MatLab's 

[~, ~, W] = eig(A);

in Maple as verbatim as possible? 
Note that MatLab's help page claims: 

Hello, I'm trying to automate a series of priority calculation exercises. I have a problem with the "/" and " " division symbols. The "Parse" command only accepts "/" .Thanks for your insights

PEMDASTest.mw

Assume

a:=2 m

b:=3 m

I will then calculate A as a times b, but Maple just gives med the answer 6 m².

I would like the output to become:

A = a * b = 2 m * 3 m = 6 m²   (with * as normal multiplication-dots)

It is possible to write at proc with the above output? It should work for any expression.

The argument of the function should just be the name of the expression. Fx:

showCalculateProc(A)

The showCalculateProc(A) should then give the output

A = a * b = 2 m * 3 m = 6 m²         (with * as normal multiplication-dots)

I know about InertForm[NoSimpl], but it doesn't do all I want it to do, and not so nice output (* as multipliction)

Thanks.

With the context-panel

How to format all occurences of numbers?

Download Number_Format.mw

Dear Maple   help me to  to plot the graph please see and rectify.  thanks in advance

i am attaching the codes 

inf:=5:
pdes:= R(X,R,t)*diff(U(X,R,t),X)+U(X,R,t)*diff(R(X,R,t),X)+R(X,R,t)*diff(V(X,R,t),R)+V(X,R,t),
         diff(U(X,R,t),t)+U(X,R,t)*diff(U(X,R,t),X)+V(X,R,t)*diff(U(X,R,t),R)=Gr*T(X,R,t)+Gc*C(X,R,t)+(1/R(X,R,t))*diff(R*diff(U(X,R,t),R),R),
         diff(T(X,R,t),t)+U(X,R,t)*diff(T(X,R,t),X)+V(X,R,t)*diff(T(X,R,t),R)+(1/(Pr*R(X,R,t)))*diff(R*diff(T(X,R,t),R),R),diff(C(X,R,t),t)+U* diff(C(X,R,t),X)+V(X,R,t)*diff(C(X,R,t),R)+(1/(Sc*R(X,R,t)))*diff(R*diff(C(X,R,t),R),R):
conds:= U(X,R,0)=0, V(X,R,0)=0, T(X,R,0)=0,  C(X,R,0)=0,                                            
        U(X,1,t)=1, V(X,1,t)=0, T(X,1,t)=1,  C(X,1,t)=1,                                                                          U(0,R,t)=0, T(0,R,t)=0, C(0,R,t)=0,
        U(X,int,t)=0,T(X,int,t)=0,C(X,int,t)=0:
pars:= { Gr=5, Gc=10,Sc=2.0}        

              pars := {Gc = 10, Gr = 5, Sc = 2.0}

PrVals:=[0.71, 1.00, 1.25, 2.00]:
  colors:=[red, green, blue, black]:
  for j from 1 to numelems(PrVals) do
      pars1:=`union`( pars, {Pr=PrVals[j]}):
      pdSol:= pdsolve( eval([pdes], pars1),
                       eval([conds], pars1),
                       numeric
                     );
      plt[j]:=pdSol:-plot( U(X,R,t),X=1, t=2, R=0..inf, numpoints=200, color=colors[j]);
  od:
  plots:-display( [seq(plt[j], j=1..numelems(PrVals))]);

I have expressions with head Sum that are all either one single Sum or sum of these Sum's. So my expression is either

Sum(.....)+Sum(....)+Sum(...)   or Sum()  

Inside each Sum, I have indexed a[n] and also possibly nonindexed a For an example

             Sum( a[n]*x + a, n=1..10)

And I want to change all the indexed a[n] to b[n] 

Hence the example above it will becomes  Sum( b[n]*x + a, n=1..10)

I can't just use eval(expr,a=b) as that will also change the non-indexed a to b which I want to leave as is. There will be only one single indexed variable in the sum. In this example it is `a`

Below is a general example and my solution. I'd like to find if there is a more canonical way or shorter more direct way to do this in Maple. 

restart;
expr:=Sum(x^(n+r)*a[n]*(n+r)*(n+r-1)+a[n-1]+3*a*x^10,n = 0 .. infinity)+Sum(4*a*x^(n+r)*a[n],n = 0 .. infinity)+Sum(4*a[n-1]*x^(n+r)+a[n]*x+a*x,n = 1 .. infinity) = 0;

evalindets(expr,specfunc( anything, 'Sum' ),f->Sum(evalindets(op(1,f),'indexed',ff->b[op(ff)]),op(2,f)))

I used evalindets twice. Once to look for Sum, and then to look for 'indexed' within each sum. It seems to work. Here is screen shot of the output

If you asking why I have indexed a and non indexed a in the same expression? Well, it is because the non-indexed a happend to be a coefficient of the ode that the user used. So it is part of the input, which I have no control over. But the indexed a is a local variable I am using inside the function being called to process the input.

On the screen they look the same. But they are actually not the same. The indexed a is local to the function and the non-indexed a is input via argument. So it is global symbol. 

What is Ei1 in Maple?

Download Ei1.mw

How I can plot a volumetric body with the coordinates provided in the text file attachment?

after finding the geometry curve I want to find the curve that passes through the middle source.

1.txt

Can someone explain how to use Maple to get from Eq. (4) to Eq. (5) using Eq. (6) to (8)?

This is the Peng Robinson Equation of State (1976)

I tried some stuff like using algsubs  on Eq. (4) and then do some polynomial operations (expand, collect etc.) It did not work out though. I'm grateful for any advice!

After I switched to using arrows = curve in the call to DEtools:-DEplot I found errors in some calls. 

Is there a workaround other than not using this option? As phase plot looks like better with this option. For now, I will remove this option.

Here is an example

restart;

ode:=diff(y(x),x)-1/(-x^2+1)^(1/2) = 0;
x_range:=-0.99 .. 0.99;
DEtools:-DEplot(ode,y(x),x =x_range,y = -1.6 .. 1.6,[y(0) = 0],arrows = 'curve')

Error, (in DEtools/DEplot/direction) cannot assign a complex value to a hardware float Array

But this works

restart;

ode:=diff(y(x),x)-1/(-x^2+1)^(1/2) = 0;
x_range:=-0.99 .. 0.99;
DEtools:-DEplot(ode,y(x),x =x_range,y = -1.6 .. 1.6,[y(0) = 0])

I will report this to Maplesoft as it looks like a bug to me. 

May be someone can find a workaround so I can use arrows = curve?

Maple 2023.2 on windows 10

Download detools_deplot_arrows_curve_problem_NOV_10_2023.mw

I recently answered a question concerning the Lane-Emden equation (see here LaneEmden) where the main topic was about finding its numerical solution.

The generic form of the Lane-Emden equation with parameter n is

LaneEmden := n -> (Diff(xi^2*(Diff(theta(xi), xi)), xi)) = -theta(xi)^n * xi^2

      d   /  2 / d            \\             n   2
n -> ---- |xi  |---- theta(xi)|| = -theta(xi)  xi 
      dxi \    \ dxi          //                  

I have just realized that I missed a "small" point in the original question: the OP ( @shashi598 ) wrote
"[...] Maple never comes out of evaluating [the] analytical solution when n=5 [...] ".
The important point here is that this solution (at least for some initial conditions) is known and simple (in the sense it doen't involve any special function).

So I tried for a few hours to verify this claim, and ended wondering myself if it might not be right?

Could you please tell me (I guess @shashi598 would be interested too in your return) if the differential equation LaneEmden(5) can be solved formally?
TIA.

Emden_equation.mw


EDITED:
After a little research it seems that very specigic method are used to build the analytic solution of the LaneEmden(n) (n not equal to 0, 1 and 5): serie expansions, homotopy, Adomian decomposition for instance.
I wasn't capable to find how the solution for LaneEmden(5) have been got for the first time (iseems to be atthe end of the 19th century).

Hello everyone, 

Can someone help me how to use a Matrix in sum?

Thanks

how I can find the solution of differential equations with dsolve?

Thesis_(1).mw

Download Thesis_(1).mw