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I have a Matrix of data points I am plotting using plots:-listdensityplot. That works fine.

However, the axes are labeled by row and column number of the Matrix (e.g. 1..20 or whatever). In reality, these are of course some parameters the range of which has been mapped onto the rows and columns of the Matrix.

How can I display the axes using the values of the original parameters? I know the transformation from Matrix row or column to the actual parameters (and in this case it is linear).

TIA,

Mac Dude

 

Hi experts,

the standard resolution for maple contourplots is 72 dpi wich is not suitable for publication purposes. I need at least a resolution between 500 - 1000 dpi. How do I get better resolutions for my contourplots when exporting them to .bmp or .jpg-files?
Somebody any ideas?

Consider the differential equation   d/dx y(x)=2*y(x)*(y(x)-4), on the rectangle -1 < x < 1, -2 < y < 7.40 in the xy-plane.

(a) Use DEplot to plot the direction field for the differential equation on the given domain. Assign your answer to my_plot_1.

restart: with(DEtools):
DEexp1:=2*y(x)*(y(x)-4);

DE:=Diff(y(x),x)=DEexp1;


DEplot(DE, y(x), x=-1..1, y=-2..7.4);
Error, (in DEtools/DEplot/CheckDE) derivatives must be given explicitly

 

Thanks for your help!

Level: Idiot (Me)

I have a matrix of 3 columns and lots of rows M

  • First column is latitude in degrees
  • Second column is longitude in degrees
  • Third column is data

So I set lambda:=M(..,1) and phi_g:=M(..,2) giving me two column vectors.

I want to convert lambda and phi_g to polar coordinates theta and phi

theta:=90-lambda produces "Error, (in rtable/Sum) invalid arguments"

WHY?

I also want to convert phi_g to phi where phi=phi_g when phi_g is 0...180 and phi=phi_g +360 when phi_g <0

How do I create a conditional function like this?

How can I get the Automorphism Group of a group G as a Permutationgroup?

 

Best regards

 

Kurt Ewald

Hello,

this is the second time I'm writing.

I posted this question in June http://www.mapleprimes.com/questions/201781-System-Of-Parametric-Equations.

This time I have  a similar problem because I'm trying to find a solution for a parametric system of equations but the number of equations and parameters is much bigger and using the tips you gave me last time I couldn't reach any result.

Here is the system:

1) alpha[1]=v*a*u*b ;
2) alpha[2]=v*a*u*(1-b);
3) alpha[3]= v*z*c*(1-a) ;
4) alpha[4]=v*z*(1-a)*(1-c) ;
5) alpha[11]=1/2*v*a* u* b* (-p*u*b+p*u*b*a+b*g-g);
6) alpha[22]=1/2*v*a*u*(1-b)* (p u b-p u b a-b g-p u+p u a);
7) alpha[33] =1/2*v*c*z*(1-a)* (c* (-z*p*a+q)-q);
8) alpha[44]=1/2*v*z*((1-a)*(1-c)* (c*z*p*a-z*p*a-q*c);
9) alpha[12]=v*a*u*b*(1- b)*(-p*u+p*u*a+g) ;
10) alpha[13]=v*a*u*b*z*c*p*(1-a) ;
11) alpha[14]=a*u*b*z*(1-a)*(1-c) ;
12) alpha[23]=a*u*z*c*(1-a)*(1-b);
13) alpha[24]=v*a*u*z*p*(1-a)*(1-b)*(1-c);
14) alpha[34]= v*c*z*(1-a)*(1-c)*(-z*p*a+q);

 

I have 14 equations/unknowns and 8 parameters (a, b, c, u, v, z, p, q).

I would like to write this system only in terms of alphas. In order to do so, I usually try to find the value for the parameters and the substitute them into the equations (and I have already found b,c,g,q using this technique) but I couldn't manage to find all of them. 

Howveer, as you suggested me, with Maple there is the command "eliminate" that implement exactly what I'm looking for but I can't make it work.

This is my code:

> sys := {alpha[1] = v*a*u*(1-b), alpha[2] = v*a*u*b, alpha[3] = v*z*c*(1-a), alpha[4] = v*z*(1-a)*(1-c), alpha[11] = (1/2)*v*a*u*(1-b)*(p*u*b-p*u*b*a-b*g-p*u+p*u*a), alpha[12] = v*a*u*b*(1-b)*(-p*u+p*u*a+g), alpha[13] =      z*c*a*u*(1-a)*(1-b), alpha[14] = v*z*a*u*p*(1-a)*(1-b)*(1-c), alpha[22] = (1/2)*v*a*u*b*(-p*u*b+p*u*b*a+b*g-g), alpha[23] = v*z*c*a*u*b*p*(1-a), alpha[24] = z*a*u*b*(1-a)*(1-c), alpha[33] = (1/2)*v*c*z*(1-a)*(c*(-z*p*a+q)-q), alpha[34] = v*c*z*(1-a)*(1-c)*(-z*p*a+q), alpha[44] = (1/2)*v*z*(1-a)*(1-c)*(c*z*p*a-z*p*a-q*c)};

> eliminate(sys, {a,b,c, p, q, u, v, z});

> simplify(%, size);

 

I also tries to substitute in the system the four parameters I already found but still I can't find a solution.

What am I doing wrong? Or the problem is that it is too complicated?

 

Thank you for your attention,

Elena

Solve Problems ...

July 17 2014 MSac 15

Hi

I can't solve the problem to have the right solution of

solve({cos(x)!=0,x>=0,x<=2*Pi})

while solve works with

solve(cos(x)!=0)

Any ideas on why this happen?

restart:
Eq1:=r^2*diff(w(r),r$2)+r*diff(w(r),r$1)-r^2*G5*w(r)-P*r^3*G6-G7*r^3-G8*r^5+C1*r/G3=0;

res1:=dsolve(Eq1);

bcs:=D(w)(0)=0,w(h)=0;

res2:=(dsolve({Eq1,bcs},w(r)));

match(rhs(res2)=rhs(res1),r,s);

eval(_C2, s);

Any idea?

Thanks

We know that sum can return an symbolic summation, for example,

 

But sometime the relation of parameters in series cannot be defined easily. And it seems that sum cannot correctly determine the symbolic summation of this kind of series:


Maybe it's due to the value of _C(infinite) is undefined. Does anyone have good idea to compute the symbolic summation of this series?

I'd appreciate any help on this topic. Thank a lot.

sum_cannot_return_symbolic_summation.mw

Dear all,

I tried to display an animation which can zoom as the time goes.

But it seems that if I display several animations in one plot window, it will display the animation with the maximum view size from these animations, not separately display these animations with their view size.

 

There are two examples:

Case1,

a1 := animate(plot, [x^2, x = -1 .. t, view = [-1 .. 1, 0 .. 1]], t = -1 .. 1);

a2 := animate(plot, [x, x = -1 .. t, view = [-1 .. 1, -1 .. 1]], t = -1 .. 1);

display(a1, a2);

 

Case2,

animate(plot, [x^2, x = -1 .. 1, view = [t .. 1, 0 .. 1]], t = 0 .. -1)


Is it possible to zoom the animation with time? What parameter should I set?

The related maple file is attached.

zoom_animation_with_time.mw

suppose W1 is weight matrix of graph G1 and W2 is weight matrix of graph G2 (G1 and G2 has same vertices and same edges but with different edge weights)

we want to create graph G3 that has a weight matrix W3. suppose w3[i][j] is an element of W3. we must have :

w3[i][j]=max(w1[i][j],w2[i][j])

w1[i][j] and w2[i][j] are elements of W1 and W2,respectively.

how can we create such graph G3 ?

When I enter the following code from the help file:

 

textplot3d([[1,2,3,"antelope", 'font'=["times","roman",20]], [3,2,1,"tiger"]], 'axes'='boxed', 'view'=[0..4, 0..4, 0..4]);

 

I receive the error message:

Plotting error, invalid FONT specification

I am trying to reduce the font size to fit many closely spaced strings in the plot.

Can anyone help.  I am running maple 16 on  Windows 7 machine.

Dear all, 

I'm trying to extract the coefficients from the equation below, the fat expressions in the equation. I don't have any trouble seperating the sine or cosine functions. But the constants are a problem. Since t is the only variable in the function i tried, coeff(R, t, 0). This does not work apparantly. Any suggestions? 

 

R:=(1/12)*C2^3*cos(2*t) - (1/48)*C2^3*cos(4*t) - C2^3*sin(t) + C2^3*sin(3*t)-C2^2*C4*cos(t) + C2^2*C4*cos(3*t) - (1/8)*C2^2*C4*sin(2*t) + (1/16)*C2^2*C4*sin(4*t) + (1/16)*C2*C4^2*cos(4*t) - C2*C4^2*sin(t) - C2*C4^2*sin(3*t) - C4^3*cos(t) - C4^3*cos(3*t) - (1/24)*C4^3*sin(2*t) - (1/48)*C4^3*sin(4*t) - (1/16)*C2^3 - (1/16)*C2*C4^2 - (1/2)*C2*cos(2*t) + C2*sin(t) + C4*cos(t) + (1/2)*C4*sin(2*t) + (1/2)*C2

It says at

http://www.maplesoft.com/products/maple/new_features/maple18/Language_Programming.aspx#random

"When generating matrices and vectors of floats and integers, these flavors are very fast. "

But when I compare the new

time[real](Generate(('Matrix')(float, 300, 300)))

and

time[real](RandomMatrix(300, 300))

I find RandomMatrix over 300 times faster. Am I doing something wrong, or is RandomMatrix still the fastest way to generate random numbers?

 

 

Hello everyone,

i'm trying to simulate a diffusion problem. It contains two connected regions in which a species is diffusing at different speeds. In one region (zeta) one boundary is set to be constant whereas in the other region (c) there is some oscillation at the boundary.The code i try to use is as follows:

sys1 := [diff(c(x, t), t) = gDiffusion*10^5*diff(c(x, t), x$2), diff(zeta(x, t), t) = KDiffusion*10^6*diff(zeta(x, t), x$2)]

pds := pdsolve(sys1, IBC, numeric, time = t, range = 0 .. 3000, spacestep = 3)

However the main problem are my boundary conditions:

IBC := {c(0, t) = 0, c(x > 0, 0) = 0, zeta(0, t) = .4, zeta(x > 0, 0) = .4, (D[1](c))(3000, t) = sin((1/100)*t), (D[1](zeta))(0, t) = 0}

Like this it principally works (however it is apparently ill-posed).

Now what i do like is that the two equations are coupled at x=2000 with the condition that c(2000,t)=zeta(2000,t). This however i dont seem to be able to implement.

I appreciate your comments

Goon

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