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

Hello.

Two related questions: I'd like to measure the CPU time used by a computation. Should I use with(CodeTools)? or use  time[real]? What would be the most accurate way to measure the CPU time used by one call, say dsolve()?

Also, How would one return both the result of the computation and the time used in one call so that one does not have to make two separate calls: to obtain the result and to obtain the CPU time?

Example:

restart;
with(CodeTools):
ode:=2*a*x^3*y(x)^3+2*x*y(x)+diff(y(x), x);
result:=Usage(dsolve(ode=0,y(x)),output='cputime');

Gives result:=0.141 while

restart;
ode:=2*a*x^3*y(x)^3+2*x*y(x)+diff(y(x), x);
result:=time[real](dsolve(ode=0,y(x)));

Gives result:= 0.145

But in both cases, I have to make another call to get the result of the DSolve in this example. result:=dsolve(ode=0,y(x)); which I'd like to avoid if possible. 

I am using Maple 18

I'm not being notified anymore about responses to answers or comments to MaplePrimes. I'm assuming that I'm not the only one (?). This has happened before.

Hello, everyone.

There are two variables: n1 and n2, how to define n1+n2=1 (not n1:=1-n2).

Thanks!!

I have a Maple program that fits a nonlinear function with 9 parameters to a dataset that contains multiple records; each record gets fitted separately. The records are ordered by a certain experimental variable (an angle of a target). The initial parameters for each fit are the solutions of the previous fit; in this case I get relatively good initial estimates and not too much trouble fitting. I use Statistics:-NonLinearFit to do the actual fitting.

Since this is a bit time consuming and I need to do this a fair amount of times, I'd like to see if I can't speed his up by employing parallel programming.

One way to speed up a fit is to compute the sum of residuals in parallel; is there a way to do this in Maple?

Another way would be to run several fits at the same time. The problem I have with that in this case is that I use the results of the previous fit as starting values for the next fit. I might be able to increase the stride of this scheme; i.e. for 4 processes, use the result of fit 1 as starting point for fit 5; fit 2 for fit 6 etc. But before I embark on this non-trivial change; can Statistics:-NonLinearFit even be used in this way (i.e. is it thread safe)?? My fitting function is an actual function (as opposed to a procedure with local variables) so I don't think the function itself would cause trouble.

I could also contemplate the Grid package; except that I am concerned about the overhead moving the data over to each node (although it would all sit on one machine with 4 processors).

I realize that I may have to do some experimentation by myself, but if there is any experience out there I'd like to know about it...

Mac Dude

Everytime I re-run a workfile, I get several extra editing lines inbetween my own command lines. Have I missed something in my settings?

Best regards
Emilijan Vuletici

task:

Use DEplot to sketch a direction field for my_deq and the solution curve for the initial condition T(0) = 88 C. Assign your plot to my_plot.

*Note: my_deq is the differential equation 

My input:

ODE2:=(Diff(T(t), t) = 1/59*(18-T(t)));

DEplot( ODE2, T(t), t=-4..4, {[T(0)=88]}, y=0..100);

Error Received: 

Error, (in DEtools/DEplot/CheckInitial) the 'number' option must be specified before initial conditions

The only thing I can find about this error is the input isn't in the form of a differential equation... But I'm pretty sure it is.

Thanks!

Basically I have to find omega by solving determinant of the following matrix:

M := Matrix(4, 4, {(1, 1) = 0, (1, 2) = -1, (1, 3) = 0, (1, 4) = 1, (2, 1) = -EI*beta^3, (2, 2) = -m*omega^2, (2, 3) = EI*beta^3, (2, 4) = -m*omega^2, (3, 1) = EI*sin(147*beta)*beta+k_r*cos(147*beta)+I*c_r*omega*cos(147*beta), (3, 2) = EI*cos(147*beta)*beta-k_r*sin(147*beta)-I*c_r*omega*sin(147*beta), (3, 3) = -EI*sinh(147*beta)*beta+k_r*cosh(147*beta)+I*c_r*omega*cosh(147*beta), (3, 4) = -EI*cosh(147*beta)*beta+k_r*sinh(147*beta)+I*c_r*omega*sinh(147*beta), (4, 1) = -EI*cos(147*beta)*beta^3+sin(147*beta)*k_h, (4, 2) = EI*sin(147*beta)*beta^3+cos(147*beta)*k_h, (4, 3) = EI*cosh(147*beta)*beta^3+sinh(147*beta)*k_h, (4, 4) = EI*sinh(147*beta)*beta^3+cosh(147*beta)*k_h}):

The remaining values are:

beta=((5000/10^12)*(omega^2))^(1/4),k_r=3.33*10^10,k_h=1.62*10^9,c_r=3.14*10^9,m=350000,L=147,EI=10^12:

What is the proper way to deal with this problem numerically. Or maybe it is even possible to get a reasonable analytical expression?

Maple evaluates

Int(ln(1+x)/(1+x^2),x=0..1);

as

1/2*I*dilog(1/2+1/2*I)-1/2*I*dilog(1/2-1/2*I)+1/4*Pi*ln(2)-Catalan

It would be nice if Maple could simplify this to 1/8*Pi*ln(2). If you evalf the integral and use "identify" then Maple does return 1/8*Pi*ln(2).

MMa directly returns 1/8*Pi*ln(2), which seems preferable.

Hello everyone.

I have a vector field in 2d-cartesian coordinates which I would like to convert to a "normal" function, that is f(x, y) where when you put x and y in, you get the magnitude of the vector at that point.

Example vector field:

This one is very hard to handle by hand which is why I want to use Maple for it.

I tried VectorCalculus[Norm] but it gave me this:

my int is in below.

my_int.mw

my int has hyperbolic and trigonal parts thus when they are multiplied , Maple is not able to integrate!

Now, How can I solve this integral?

thank you for help

my int is: