# Items tagged with variablesvariables Tagged Items Feed

### Change of variables in differential equation...

December 03 2013
1 2

Consider the differential equation zZ'' + Z' + a2Z = 0,  where Z = Z(z).  Using the change of variables x = \sqrt{z/b}with b a constant,  obtain the differential equation Z'' + (1/x)Z' + c2Z = 0, where Z = Z(x) and c = 2a \sqrt{b}.

I tried Maple help and it offers the dchange command, and what I have tried is shown below;

with(PDEtools):

DE:= ...

tr:= {z = x2b}

dchange(tr, DE)

This did not return anything however.  I am thinking I need to specify that b is a constant, however, I am a little unsure on how to do this. Is the above the correct way to proceed?  I don't see how I have specified anywhere that in the final PDE, I require Z=Z(x).

Thanks for any help.  This is my first post here, so apologies for the typesetting. If there is inbuilt latex, I will use it next time.

### Variables do not define...

November 16 2013
1 5

The purpose is to display the projection of a 3D plane, defined by the points of P. "res" contains the points projected on a 2D plane and all variables beginning with "vlak" contain the points from res that should be connected to form a plane. The command polygonplot connects the points. Every time, it gives the error message "Error, (in plots:-polygonplot) points are not in the correct format". When I copy the code to a place outside the procedure, I discovered some variables are not defined.

restart:with(linalg):with(LinearAlgebra):with(VectorCalculus):with(plots): eerste:=proc(V,N,P) local M,M1,M2,I4,NT; NT:=Transpose(N); M1:=V.NT; I4:=IdentityMatrix(4); M2:=(N.V).I4; M:=M1-M2; M.P; end proc: tweede:=proc(OS,r,s,P1) local VC,K: K:=Matrix(4,3,[r,s,OS]); VC:=(MatrixInverse(Transpose(K).K)).Transpose(K); VC.P1; end proc: project:=proc(P,V,N,OS,r,s) local P1,P2,i,j,n: P1:=eerste(V,N,P); P2:=tweede(OS,r,s,P1); n:=ColumnDimension(P2); for i from 1 to n do for j from 1 to 2 do P2[j,i]:=P2[j,i]/P2[3,i]; end do: end do: DeleteRow(P2,3); end proc: P:=Matrix([[ 0 , 10 , 10 , 0 , 0 , 10 , 10 , 0 , 5 ], [ 0 , 0 , 10 , 10 , 0 , 0 , 10 , 10 , 5 ], [ 0 , 0 , 0 , 0 , 30 , 30 , 30 , 30 , 40 ], [ 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 , 1 ]]): V:=Vector([60,60,50,1]); N:=Vector([1,0,0,0]); OS:=Vector([10,10,0,1]); r:=Vector([0,1,0,0]); s:=Vector([0,0,1,0]); Vector[column](%id = 18446744073889448174) Vector[column](%id = 18446744073889448414) Vector[column](%id = 18446744073889448534) Vector[column](%id = 18446744073889448654) Vector[column](%id = 18446744073889448774) translatie:=t->Matrix([[ 1 , 0 , 0 , 1*t ], [ 0 , 1 , 0 , 1*t ], [ 0 , 0 , 1 , 0 ], [ 0 , 0 , 0 , 1 ]]); [1 0 0 VectorCalculus:-*(1, t)] [ ] [0 1 0 VectorCalculus:-*(1, t)] t -> [ ] [0 0 1 0 ] [ ] [0 0 0 1 ] f:=proc(t) local volgende,res,vlak_onder,vlak_links,vlak_voor,vlak_rechts,vlak_boven,vlak_achter,vlak1,vlak2,vlak3,vlak4,pp1,pp2,pp3,pp4,pp5,pp6,pp7,pp8,pp9,pp10: volgende:=MatrixMatrixMultiply(translatie(t),P): res:=project(volgende,V,N,OS,r,s): vlak_onder :=Transpose(Matrix([Column(res,1),Column(res,2),Column(res,3),Column(res,4)])): vlak_links :=Transpose(Matrix([Column(res,1),Column(res,2),Column(res,6),Column(res,5)])): vlak_voor :=Transpose(Matrix([Column(res,2),Column(res,3),Column(res,7),Column(res,6)])): vlak_rechts:=Transpose(Matrix([Column(res,3),Column(res,4),Column(res,8),Column(res,7)])): vlak_achter:=Transpose(Matrix([Column(res,1),Column(res,4),Column(res,8),Column(res,5)])): vlak_boven :=Transpose(Matrix([Column(res,5),Column(res,6),Column(res,7),Column(res,8)])): vlak1:=Transpose(Matrix([Column(res,8),Column(res,7),Column(res,9)])): vlak2:=Transpose(Matrix([Column(res,8),Column(res,7),Column(res,9)])); vlak3:=Transpose(Matrix([Column(res,8),Column(res,5),Column(res,9)])); vlak4:=Transpose(Matrix([Column(res,5),Column(res,6),Column(res,9)])); pp1:=polygonplot(vlak_onder): pp2:=polygonplot(vlak_links): pp3:=polygonplot(vlak_voor): pp4:=polygonplot(vlak_rechts): pp5:=polygonplot(vlak_achter): pp6:=polygonplot(vlak_boven); pp7:=polygonplot(vlak1); pp8:=polygonplot(vlak2); pp9:=polygonplot(vlak3); pp10:=polygonplot(vlak4); {pp1,pp2,pp3,pp4,pp5,pp6,pp7,pp8,pp9,pp10}: end proc: display(f(0),scaling=constrained); Error, (in plots:-polygonplot) points are not in the correct format

Above, you can see the code. When only pp1->pp7 is displayed, and pp8->pp10 is placed between commenting marks, it works fine. Otherwise it doesn't work, it looks like Maple does not define the variables pp8->pp10. I don't understand because there is no difference between pp7 and pp8.

### How to include constant variables in summation and...

August 11 2013
1 2

Dear all,

I'm trying to substitute a combination of variables in an equation that is partly covered in a summation.

For example consider the equation with two variables A and B, and two function W(t) and q(z):

now I want to do the substitution:

### Procedure variables...

July 15 2013
0 1
Hi, I am hoving trouble understanding how variables are meant to be declared. I have global variables that I wish to use that are tabled values such as m[1], ie: m subscript 1.However, when declaring parameters, local, or global variables within a procedure it does not allow them to be tables values. Why is this? and How should i be declaring these values?for example:Range:=proc(b[1]).... b subscript 1 will generate invalid parameter declarationRange:=proc(b) local c[1]...c subscript...

### A typographical issue with the new subscripts...

March 26 2013 Maple 17
4 11

Dear Maple Users

I am mainly in favor of the new rules concerning subscripts. Using Ctrl+-- (double underscore) it is pretty straight forward to get a literal subscript and it displays much better in the palette Variables than was the case i Maple 16. Also the purple coloring of a variable containing a literal subscript makes sense, because it can be distinguished from the usual subscript (now Ctrl+shift+-). Good that you can remove the coloring in the View Menu (Atomic Variables...

### unknown number of parameters...

March 25 2013
0 7

Hi

i want to minimizez the "Eq1(h[1],h[2],...h[n])" for all the h[i] in the ranges of -1<h[i]<1.  "n" (number of unknown variables) can be determined during the code and was not know before. how can i do this?

It must be stated that when i have Eq1 and two unknown variables such as h[1] and h[2], i wrote the following code and it works good, but i dont know how can i write mentioned command for unknown number of variables.

NLPSolve(Eq1,h[1]=-1..1,h[2]=-1..1);

### list of memory usage of variables in workspace...

February 05 2013
1 14

Hi,

is there any analogous command to whos in Matlab to list the memory usage of specific variables in workspace?

Thanks!

Bye

Tom

### how to plot multiple variables for system of nonli...

December 09 2012
0 4

hi everyone,

I need to plot a graph for system of nonlinear equations with multiple variables.

here is some example of system nonlinear

f4=c^2+d^2-1=0

with initial condition (0.7, 0.2, 0.6, 0.3)t. I solved this using Newton's method and here the iteration

### Can I set a default for assume ?...

November 15 2012
0 4

In economics, variables are always real and often positive.

With assume(x>=0) I can set this for individual variables. But with many variables it is arduous.

Is it possible to set by default all variables to >=0 and define ony the exceptions individually?

Thanks you !

### How do I extract the corresponding variables given...

November 04 2012
0 2

I have a multivariate polynomial equation, in that somehow I know the coeffcients, using this information, I want to extract the variables. This will be the opposite of coeffs function.

for e.g. I have 3*x3 + 5*x4

Given 3 and 5, I want to extract x3 and x4.

Satya

### Plotting two functions of 2 variables in maple...

October 27 2012
0 2

I am trying to plot (3-Dimensional) two functions of 2 variables in maple. Here is my code:

K := (V, E) --> E*log(V)P:= (V, E) --> E + V*log(V)
with(plots):
plot(K(V, E), P(V,E), V = 0 .. 20, E = 0 .. 190)               /*This line does not work*/
I want a 3D plot where a point in the graph would be: (K(V, E), V, E)

1. How can I plot a 3-Dimensional Plot of two functions with 2 variables?

### Problem with assign and local variables....

June 10 2012
0 3

Hello,

How can I use assign(...) inside in proc in order to affect the local variables and not the globals.

Thanks

### symbolic manipulation mod 2...

June 01 2012
1 1

I want to be able to create expressions in the two noncommutative variables a and b such that an expression

(b+a)*a +ba symplifies to a*a. Thus the first expression expands to ba+aa, which when added to ba

yields ba+aa+ba=aa.

How to arrange for this will be greatly appreciated.

### What am I doing wrong? (for loop)...

April 15 2012
0 2

Dear Maple users

I am having a problem with a simple for loop. I cannot seem to figure out what is wrong. I want to define a number of Random Variables of the ChiSquare kind, with increasing number of degrees of freedom as the figure below suggest. When defining them one line after another everything works well. My idea was then to make a for loop, since I might want many Random Variables defined. It doesn't work however in the way I do it. All...

### how can i define variables 'omega' and 'omega[n]' ...

March 26 2012
0 3

i define two variables as follow:

restart:

omega:=1

omega[i]:=2

i find the 'omega' i had defined  renewd by

omega:=table[i=1]

then type:

omega,omega[i]

result is:    omega, 2

how can i define these two variables in one worksheet?

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