Maple Questions and Posts

These are Posts and Questions associated with the product, Maple

Hello, 
I have this problem to my system:

sol := pdsolve(sys2, {bcs, ics}, numeric)
sol:-plot3d(u1(x, t), x = 2 .. 3.2, t = 100 .. 1000)
Error, (in pdsolve/numeric/plot3d) unable to compute solution for t>HFloat(0.0):
unable to store HFloat(undefined)+HFloat(undefined)*I when datatype=float[8]

It is 1 pde and 1 ode.

What can I do to solve it?


Best
 

Dear Maple community,

I am trying to solve a system of linear equations, each of which is homogenous of degree 1 (i.e., defined up to a scale/constant factor), and was wondering whether one can use Maple to solve for ratios of variables (defined relative to a numeraire). An example of my problem is attached (Example.mw). More specifically:

- Equation (1) defines the system,

- Equations (2) through (4) exemplify the system for J=3 and S=1 (creating the system of 3 equations in 3 unknowns: {dlog R[1,1], dlog R[2,1], dlog R[3,1]},

- Function A solves this system for the unknowns and the subsequent commands simplify dlog R[1,1] (and dlog R[2,1]) using the model's constraints (side relations). Not surprizingly, I get the error message "Error, (in simplify/siderels:-Recurse) indeterminate expression of the form 0/0", which results from the fact that the system is homogenous of degree 1 (and, hence, each dlog R is defined only up to a scale),

- However, in principle, it should be possible to choose one of the dlog R's, say, dlog R[1,1] as a numeraire and express the other two "unknowns" (dlog R[2,1], and dlog R[3,1]), relative to it, in order to ultimately solve this system for dlog R[2,1]/dlog R[1,1] and dlog R[3,1]/dlog R[1,1] as functions of exogenous variables only.

I'd appreciate any advice how I can use Maple to tackle this problem. Thank you very much in advance!

 

Hi all,

There is issue with saving big numbers to txt file on WIndows

Please look at the file:

txt_issue.mw

Function save just cutting a big number.

Thank you.

Hi, Maple seems to automatically sort my list in some numerical order. Is there a way to overcome this? I want my list as it is.

 

Hello, 

I'm trying to calculate the convolution of the radiation forve in the time domain. I need to do a state space representation of a function K(t), where :

t=[0; 1; 2; 3];

k=[0.1; 0.2; 0.3; 0.4];

If you could help me with finding the appropriate command that give the matrix A, B C and D

just a remarque that in matlab used imp2ss (based on the Hankel SVD method)

thanks

Hello there, 

Is there any way to make the equation 'Given_eq_3_37a' in the calculation below to be 'desired'?

Perhaps, the issue of the 'L__1' and '1/L__1' might have been in the way, but perhaps that might be overcome in a different way. 

Thank you, 

In Kwon Park 


 

restart;

Given_eq_3_37 := M = k_ * sqrt(L__1 * L__2);

M = k_*(L__1*L__2)^(1/2)

(1)

Given_eq_3_30 := k_ = sqrt((L__m)^2 / (L__1 * L__2p));

k_ = (L__m^2/(L__1*L__2p))^(1/2)

(2)

Given_eq_3_37a := simplify(subs([Given_eq_3_30], Given_eq_3_37));

M = (L__m^2/(L__1*L__2p))^(1/2)*(L__1*L__2)^(1/2)

(3)

desired := M = sqrt(L__m^2/(L__1*L__2p)*(L__1*L__2));

M = (L__m^2*L__2/L__2p)^(1/2)

(4)

 


 

Download Q20201001.mw

Hello everyone. I want to know how I can extract terms from a multivariate polynomial with the following 2 conditions:

  1. It should have the lowest sum of the degree of x and of y; and
  2. deg(x) - deg(y) should be either 0 or -1.

For instance, if I've f(x) = 100x^2y^2 + 35yx + 45x, I want an output of 35yx (not 45x; even though degree sum is 1, less than 2).

On the other hand, if I've g(x) = 13x^2y^2 + xy^2 + 2yx^2, I want an output of xy^2 (not yx^2 also).

Hello everyone, I have some weird problems with the maple. The problems are different for the document mode and the worksheet mode, however I strongly believe that they are connected. Starting with the document mode:

I simply cannot execute any command with the symbolic notation. As you can see below, I can execute basic mathematical calculations but I can't do any symbolic math. 


On the other hand, I can execute all the commands in the worksheet mode. For example check the screenshot. 
However, when I try to save that file in the worksheet mode, I get this error:

And, when I close the file and re-open again, I find all the stuff I wrote in the "math mode" disappeared 

 

In the worksheet below, variable x can be returned to type name after being assigned a value , but concatenated variable name A||1 cannot. Is there a way to return a concatenated variable to type name after it has been assigned a value, so it can be re-used as an unknown in solve commands?

Concatenate_Question.mw

 

Hello Everyone,

I have an equation system which is under-determined and thus yields infinite solutions. 
These usually come in the form of "_t1[1]" or similar variables. Mostly one, sometimes even two.
I am also working on a script for automated solving of a buckling problem and the solution yields of course these t-variables.
Everytime the code run, I get a different t-variable, which makes automation harder.

Please see attached code. (Of course simplified, not my actual code.)

It starts with a random matrix and a solution vector for the equation system.
The system is solved and its coefficients transfered to an equation.
However every time I hit "Enter" on the LinearSolve command, the name of the _t4[1] variable changes.

Is there a way to keep getting the same variable name? How do you work with this?

Best Regards,
Lennart

A := Matrix(4, 4, {(1, 1) = 1, (1, 2) = 3, (1, 3) = 4.5, (1, 4) = 7, (2, 1) = 0, (2, 2) = 2, (2, 3) = 5, (2, 4) = 9, (3, 1) = 0, (3, 2) = 0, (3, 3) = 0, (3, 4) = 0, (4, 1) = 0, (4, 2) = 0, (4, 3) = 0, (4, 4) = 0}); B := Vector(4, {(1) = 0, (2) = 0, (3) = 0, (4) = 0}); C := LinearAlgebra[LinearSolve](A, B)

Vector[column](%id = 18446746248681490062)

(1)

W1 := C[1]; W2 := C[2]; W3 := C[3]; W4 := C[4]; Q := W1*x^4+W2*x^3+W3*x^2+W1

(HFloat(3.0)*_t4[2]+HFloat(6.5)*_t4[1])*x^4+(-HFloat(2.5)*_t4[2]-HFloat(4.5)*_t4[1])*x^3+_t4[2]*x^2+HFloat(3.0)*_t4[2]+HFloat(6.5)*_t4[1]

(2)

restart

``


 

Download MultipleTCoefficients.mw

when i solve adomian polynomials there is a derivative withrespect to t and then put t is equal to zero. now i have to find the dervative of function with respect to t but it is already equals to zero. and i change the variable the Df could not b solved.
 

restart

with(LinearAlgebra):

F(u[i]) := u[i]^2:

NULL

for n from 0 while n <= 6 do F(u[n]) := x[n]^2; V[n] := (diff(F(sum(t^i*u[i], i = 0 .. n)), [`$`(t, n)]))/factorial(n) end do:

t := 0;

0

(1)

for i from 0 while i <= n-1 do A[i] := V[i] end do;

x[0]^2

 

(D(F))(u[0])*u[1]

 

(1/2)*((D@@2)(F))(u[0])*u[1]^2+(D(F))(u[0])*u[2]

 

(1/6)*((D@@3)(F))(u[0])*u[1]^3+((D@@2)(F))(u[0])*u[1]*u[2]+(D(F))(u[0])*u[3]

 

(1/24)*((D@@4)(F))(u[0])*u[1]^4+(1/2)*((D@@3)(F))(u[0])*u[1]^2*u[2]+(1/2)*((D@@2)(F))(u[0])*u[2]^2+((D@@2)(F))(u[0])*u[1]*u[3]+(D(F))(u[0])*u[4]

 

(1/120)*((D@@5)(F))(u[0])*u[1]^5+(1/6)*((D@@4)(F))(u[0])*u[1]^3*u[2]+(1/2)*((D@@3)(F))(u[0])*u[1]*u[2]^2+(1/2)*((D@@3)(F))(u[0])*u[1]^2*u[3]+((D@@2)(F))(u[0])*u[2]*u[3]+((D@@2)(F))(u[0])*u[1]*u[4]+(D(F))(u[0])*u[5]

 

(1/720)*((D@@6)(F))(u[0])*u[1]^6+(1/24)*((D@@5)(F))(u[0])*u[1]^4*u[2]+(1/4)*((D@@4)(F))(u[0])*u[1]^2*u[2]^2+(1/6)*((D@@4)(F))(u[0])*u[1]^3*u[3]+(1/6)*((D@@3)(F))(u[0])*u[2]^3+((D@@3)(F))(u[0])*u[1]*u[2]*u[3]+(1/2)*((D@@3)(F))(u[0])*u[1]^2*u[4]+(1/2)*((D@@2)(F))(u[0])*u[3]^2+((D@@2)(F))(u[0])*u[2]*u[4]+((D@@2)(F))(u[0])*u[1]*u[5]+(D(F))(u[0])*u[6]

(2)

NULL


 

Download Adomian_Polynomials.mw

I want to create a simple symbolic transfer function from 2 vectors, lets say:        num=<a,b,c>

                                                                                                                               den=<c,b,a,d>
So my transfer function should look like this:
              H(s) = (a*s^2 + b*s + c)/(c*s^3 + b*s^2 +a*s+d)

 

This should be very simple but I haven't found a solution on the forums yet...

Thank you.

Is it possible to develop a code for base excitation problem where excitation data is of earthquake acceleration?

p.s. There are 12000 data available in EQ file.

Hi, I have a 1D wave equation with a piecewise initial value, I am trying to plot the solution with animation, I use the below code, However, it does not give me the animation I want but give me some error, which I am not understande.

My code is following:

pde := diff(u(x, t), t $ 2) - diff(u(x, t), x $ 2) = 0

h := piecewise(-1 <= x and x <= 0, x + 2, 0 <= x and x <= 1, 2 - x, 0)

ic := u(x, 0) = h, D[2](u)(x, 0) = 0

sol := pdsolve([pde, ic])

plots[animate](plot, [sol, x = -10 .. 10], t = 0 .. 5)

and the result is showing as picture below

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