Hi, I'm working on the Smoluchowski equation (essentially the diffusion eqn with an extra derivative) diff(u(x,t),t)=k*diff(u(x,t),x)+D*diff(u(x,t),x,x) k is piecewise so the function has to be solved numerically, the boundary values are specified u(0,t)=u(1,t)=0 but i need the derivative at the boundaries D[1](0,t) and D[1](1,t). It seems to be simple to evaluate a numeric derivative of an ODE but I can't see how to do it for a PDE. Any help welcome, even some sort of brute force method if necessary. Thanks, Ryan

How do i convert a curve into its data points i.e. how can  i get the points from a curve.

Thanks

Hello,

I have a system of polynomials that I need to calculate its primedecomposition.

It has been trying for several hours but it could not give me result.

Even I tried to have Grobner basis and I could not.

Could you please let me know what should I do for that?

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I dont understand what's the 'label' thing in the answer here.

 

Thanks.

 

casper

Suppose I want a random sample of 500 numbers

RandomSample(Normal(0,1)),500);

Good, now if I am understanding properly [0,1) means positive values with a mean of 0 and standard deviation of 1.  However in Maple RandomSample(Normal[0,1)),500); is not allowed due to bracket mismatching. 

how do I get the RandomSample domain [0,1)?

Hi all I've a program running that has been stopped with the error Execution stopped: Stack limit reached. at that time the program was using memory used=480073.6MB, alloc=594.8MB, time=16330.02 The host computer has 16 CPUs and 50Gb of Ram, so I don't think the problem is the memory... Any hints? Thanks Salvo ps: I've found an old discussion about this problem, but it was very old (2005, M9) so I've thought I could open a this one.

I am trying to solve a set of 4 coupled ordinary differential equations, starting from certain set of initial conditions for certain parameter values.  i have to evolve the system for a very long time (higher number of iterates are needed).

For a certain set of initial conditions the following error occurs

"Error, (in sol12) cannot evaluate the solution further right of 2939.9221, probably a singularity"

what could be the possible way to get rid of this error.......

I'm new to programming.

I don't understand what I'm doing wrong in this

If anyone could help me with this, I'd very much appreciate it.

See the attached picture called "equation". That is the differential equation I'm trying to solve. The graph (for m=1) should like as it does in the other attached picture called "graph".

I tried this

----------------------

with(DETools):
m := 1;

de := diff(y(x), x, x, x)+((m+1)*(1/2))*y(x)*(diff(y(x), x, x))+m*(1-(diff(y(x), x))^2) = 0;

DEplot(de, y(x), x = 0 .. 8, [[y(0) = 0, (D(y))(0) = 0, (D(y))(infinity) = 1]], y = 0 .. 1);

---------------

But goes this error message

Error, (in DEtools/DEplot/CheckInitial) initial point in all initial conditions must be the same

I don't know how to get around this because my initial conditions are what they are, I can't change them.

Does anyone know of a way to fix this or know of a better way? The reason I need this is because I need to get the graph for m=0.77, which isn't in those photos.

 Any help is appreciated.

 

 

Im  writing a loop which starts by solving a circle equation,  how do i instruct maple to follow another another set of instruction if no real roots are found?

im looking to do something like this

(x1a, x1b) := fsolve((x-h)^2+(eq2-k)^2-r^2)

if real roots are found, do this

else, do something else

end if

I hope im clear enough on what im asking. If not, please let me know.

thanks

Lovinash

Hello

I have a matrix, let's call it A. I want to define a new matrix by taking every n-th row in the A matrix. How do i do that?

For example,

A= | 2 3 5 |
     | 9 2 1 |
     | 5 1 2 |
     | 1 8 9 |

 

the B, if n=2, is equal to

| 2 3 5 |
| 5 1 2 |

I'm trying to model Conway's game of Life and I keep running into the same error mesage. I've narrowed the problem down to this line of code

S0 := [[0,0,0,0],[0,1,1,0],[0,1,1,0],[0,0,0,0]];
n:=4
X:= Array(0..n-1,0..n-1,S0)
Error, bad index into Array

I don't know what this error message is or why I'm getting it, any help would be appreaciated.

Hi, sorry to post this as I have read past topics about roots but havent really understoond much.

I have an equation that gives 8 roots. some of them can be real and some can be imaginary. how do i list them separately? I attach the worksheet...

 

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Hi to all

I want know that can we slove the following equation

=0

where

F(l)= coth(l*(S0)))/coth(l*(S0-1)));

Is this possible from mathematical point of view?

 It make any sense to slove the above equation?

 

When simulating an electrical circuit I decided to eliminate a subsystem block but later changed my mind. Now I'm unable to use the same name for the subsystem block as before despite the fact that there seems to be no place where it is used. Always an error "The name blabla is already in use". Can I somehow list all the names and the places where they are used?