# Items tagged with odeode Tagged Items Feed

### Second order ODE with infinity condition...

December 15 2014
1 1

I got a problem with solving a second order ODE.

The ODE is :

-V(xi)+(1/2)*xi*(diff(V(xi), xi))+(1/4)*(diff(V(xi), xi, xi))=-(1/2)*k2*(diff(H(xi), xi))-k1*n*X/E+1+k2

where k1,k2,n,X,E  all are constant.

the condition is :

V(xi) tends to 2*xi^2 as xi tends to infinity.

I used 'dsolve' to solve the equation firstly, and got a solution with two constant C1 and C2, I want to use the condition to elimilate C2, so I used limit(sol,xi=infinity)=2*xi^2. But when I used the command 'limit', I can't get the answer.

Could any one help me?

Many thanks!!!

### How to solve non-linear ODE numerically...

December 13 2014
2 3

Hi,

I'm trying to solve the following differential equation numerically with dsolve:

but dsolve gives me this error:

> res := dsolve(DGL, numeric, parameters = [y0, A, B, C, E]);
Error, (in DEtools/convertsys) unable to convert to an explicit first-order system

I think the problem is that I use the wrong solver. Does Maple provide a solver which is capable of solving this kind of equations (nonlinear ODE)?

### Error, (in isolate) cannot isolate for a function ...

December 10 2014
0 9

Hello,

Im solving 4 ODE equations with BC. im trying to shoot the initial value but im having this error:

""Error, (in isolate) cannot isolate for a function when it appears with different arguments""

anyone could help me???

 >
 >
 >
 >
 >
 >
 >
 >
 (1)
 >
 (2)
 >
 (3)
 >
 >
 Error, (in isolate) cannot isolate for a function when it appears with different arguments
 >

December 09 2014
0 3

 (1)

 (2)

### How to plot the Taylor Polynomial approximation...

December 08 2014
0 2

Hi everyone, I have been trying to plot the Taylor Polynomial approximation with the following code. However, my maple crushes everytime I run it. I indexed some of the variables to get the plot. The code works fine without the index. What did I do wrong?

y := array(1 .. 2);

Digits := 10;

n := 30;

h := .1;

T := 0;

X := 1;

f := (x, t) -> 1/(3*x(t)-t-2);

one := 1/(3*x(t)-t-2);

two := diff(f(x, t), t);

first := diff(x(t), t)

for k to n do

y[1] := subs(t = T(k), x(T(k)) = X(k), one);

y[2] := subs(first = y[1], t = T, x(T(k)) = X(k), two);

X[k+1] := X+sum(y[i]*h^i/factorial(i), i = 1 .. 2);

T[k+1] := T+h

end do;

X[n];

data := [seq([T[n], X[n]], n = 0 .. 30)];

p[2] := plot(data, style = point, color = blue);

p[3] := plot(data, style = line, color = blue);
display(p[2],  p[3])

The code without Index (which works fine)

y := array(1 .. 2);

Digits := 10;

n := 30;

h := .1;

T := 1;

X := .1547196278;

f := (x, t) -> 1/(3*x(t)-t-2);

one := x(t)^4*e^t-(1/3)*x(t);

two := diff(f(x, t), t);

first := diff(x(t), t);

for k to n do

y[1] := subs(t = T, x(T) = X, one);

y[2] := subs(first = y[1], t = T, x(T) = X, two);

X := X+sum(y[i]*h^i/factorial(i), i = 1 .. 2);

T := T+h

end do

### Error, plot phase portrait...

November 27 2014
0 1

Dear All,

I need your help to plot the phase portrait using DEtools[DEplot]  these are the lines of the code. But when I make RUN, there is an error. I need your help to fix the error. Many thinks.

r1:=1; r2:=1; q2:=2; q1=0.5;  a1:=1;

Sys1 := {diff(N(t),t) = r1*N*(1-N/q1)-P*N/(1+N), diff(P(t),t) = r2*P*(exp(-a1*P)-q2)+P*N/(1+N)};

DEtools[DEplot](Sys1,[N(t),P(t)],t=-10..10,N=0..2,P=0..2);

Many thinks

### extracting the coefficients of an ode...

November 23 2014
1 0

I have an ode in the form:

diff(u(x),x)-f(x)=u(x)^3+B(X)*u(x)+g(x)

how to extaract and name the different coefficients of the equation?

Thanks

### dsolve is giving the error function expected...

November 22 2014
2 1

So I am brand new to using Maple and am trying to solve a system of ODE's. When I try and use dsolve however I reciever the error "function expected" and I am not sure why. The code I have is as follows

sys_ode := diff(A(t), t) = a*(A(t)+B(t))-b1*A(t)*(C(t)+D(t))-g1*A(t)*B(t), diff(B(t), t) = -b2*B(t)*(C(t)+D(t))+g1*A(t)*B(t), diff(C(t), t) = e*(b1*A(t)+b2*B(t))*C(t)-g2*b2*C(t)*B(t)-g3*C(t)*D(t), diff(D(t), t) = g2*b2*C(t)*D(t)-m*D(t)

dsolve([sys_ode])

I'm sure it is something simple, but I just can't seem to figure out where the issue is. Any help is much appreciated.

### Substituting an expression into an expression...

November 22 2014
1 1

I'm trying to substitute one Differential equation into another differential equation.

eq1:=d*n(t)/dt = (rho(t)-beta)*n(t)/Lambda+lambda*C(t)+q

eq2:=diff(eq1, t)

resulting in -> eq2 := d*(diff(n(t), t))/dt = (diff(rho(t), t))*n(t)/Lambda+(rho(t)-beta)*(diff(n(t), t))/Lambda+lambda*(diff(C(t), t))

then I'm given that (diff(C(t), t)) is given by another equation:

eq3:=d*C(t)/dt = beta*n(t)/Lambda-lambda*C(t)

At this point I'm trying to substitute equation 3 into equation 2 for diff(C(t),t)

eq4 := subs(diff(C(t), t) = rhs(eq2), eq5)

however no matter what way's I try this I get an error:

Error, (in simpl/reloprod) invalid terms in product: (d*(diff(n(t), t))/dt = (diff(rho(t), t))*n(t)/Lambda+(rho(t)-beta)*(diff(n(t), t))/Lambda+lambda*(diff(C(t), t)))^-1

I then tried to map it but again i got an error specifically about the first parameter:

Error, invalid operator parameter name

eq5:=map((d/dt C(t))->beta/Lambda*n(t)-lambda*C(t),eq2)

I'm just wondering if what I am trying to do is even possible in Maple?

If anyone can help I would greatly appreciate it!

### Error, (in dsolve/numeric/bvp) initial Newton iter...

November 10 2014
0 8

i am solving 3 ODE with boundary condition.. with boundary condition

b.mw

Maple Worksheet - Error

Failed to load the worksheet /maplenet/convert/b.mw .

then i got this error

Error, (in dsolve/numeric/bvp) initial Newton iteration is not converging

i dont know where i need to change.. could you help me..

### Solve the Coefficient of ODES ...

November 10 2014
0 1

Dear Friends,

My present problem is to calculate the coefficients

of ODES based on the experiment data. In order to simulate the actual experiment, a set of  is given with . Then the experiment data (yexp) can be calculated. Finally, the least-squares method (lsq) is used to calculate the coefficient values. Now the NLPSolve function can be used. However, the globalsolve cant run.

If it is convenient for you, wish you can solve it.

Code:

restart;
cdm_ode := diff(y1(t), t) = c0*(y6(t)*(1-y3(t))/(s0*(1-y4(t)*(1-y5(t)))))^n/(1-y2(t)), diff(y2(t), t) = ks*y2(t)^(1/3)*(1-y2(t)), diff(y3(t), t) = h1*(1-y3(t)/h2)*c0*(y6(t)*(1-y3(t))/(s0*(1-y4(t)*(1-y5(t)))))^n/(sigma*(1-y2(t))), diff(y4(t), t) = (1/3)*kp*(1-y4(t))^4, diff(y5(t), t) = A*B*y1(t)^(B-1)*c0*(y6(t)*(1-y3(t))/(s0*(1-y4(t)*(1-y5(t)))))^n/(1-y2(t)), diff(y6(t), t) = y6(t)*c0*(y6(t)*(1-y3(t))/(s0*(1-y4(t)*(1-y5(t)))))^n/(1-y2(t));

tol_t := 3600;
sol := dsolve([cdm_ode, y1(0) = 0, y2(0) = 0, y3(0) = 0, y4(0) = 0, y5(0) = 0, y6(0) = 175], numeric, range = 0 .. tol_t, output = listprocedure, parameters = [c0, n, sigma, s0, ks, h1, h2, kp, A, B]);

sol(parameters = [5.7*10^(-6), 10.186, 175, 200, 5*10^(-8), 10000, .269, 1.5*10^(-7), 1.5, 2]);

t := [seq(i^2, i = 0 .. 50, 1)];

y1data := subs(sol, y1(t));

y1exp := [seq(y1data(t[i]), i = 1 .. 51)];

err := proc (c0, n, s0, ks, h1, h2, kp, A, B) local y1cal, y1val, lsq; sol(parameters = [c0, n, 175, s0, ks, h1, h2, kp, A, B]); y1cal := subs(sol, y1(t)); y1val := [seq(y1cal(t[i]), i = 1 .. 51)]; lsq := add((y1val[i]-y1exp[i])^2, i = 1 .. 51); lsq end proc;

with(Optimization);
val := NLPSolve(err, 10^(-8) .. 10^(-4), 2 .. 20, 150 .. 250, 10^(-2) .. 1, 100 .. 20000, 10^(-5) .. .4, 10^(-5) .. 1, .5 .. 2, 1 .. 10);
GlobalSolve(err, 10^(-10) .. 10^(-4), 2 .. 20, 150 .. 250, 0 .. 1, 100 .. 15000, 0 .. .5, 0 .. 1, .5 .. 2, 1 .. 5);

Error, (in GlobalOptimization:-GlobalSolve) InertForms does not evaluate to a module

### Error, (in dsolve/numeric/bvp) initial Newton iter...

November 06 2014
0 2

i am solving 3 ODE question with boundary condition. when i running the programm i got this error.. any one could help me please.. :)

 >
 >
 (1)
 >
 (2)
 >
 (3)
 >
 (4)
 >
 (5)
 >
 Error, (in dsolve/numeric/bvp) initial Newton iteration is not converging
 >
 (6)
 >
 Warning, unable to evaluate the functions to numeric values in the region; see the plotting command's help page to ensure the calling sequence is correct
 >

### calculs using Maple...

November 01 2014
1 6

Dear all;

Thank you very much is you can make the computation using maple.

I have this system:

x'(t)=x*y-x^2*y+y^3;

y'(t)=y^2+x^3-x*y^2;

I would like to make to change the system in another system using polar coordinate: like x=r*cos(theta) and y=r*sin(theta), and then derive a simple system: r'=F(r, theta) and theta'=G(r, theta), where here F and G are two unknowns functions.

Many thinks if someone can help me using a Maple code.

### convert second order ode to first order ode.......

October 30 2014
0 2

Hi every body:

i have a second order ode and will convert to two ode of first order with maple,how do this work???

eq := diff(y(x), x, x)+2*y(x)+y(x)^2 = 0

### Solving system of ODEs whose variables come in 2 p...

October 28 2014
0 1

Let N be an integer.

For each pair of integers (n,m) where 1<= n,m <= N, we have a variable f_{n,m}(t).

Then for these we have a system of ODEs

d/dt f_{n,m}(t) = \sum_{n', m'} f_m'n' * f_m''n'' * (m'n'' - m''n')

where m''=m-m', n''=n=n', and the sum is simply over for all pairs (n',m').

I simply do not know how to put these set of equations into Maple in a nice way.

I will really appreciate any help!

 1 2 3 4 5 6 7 Last Page 3 of 21
﻿