Recently I saw a heated discussion on this post：https://www.mapleprimes.com/questions/233026-Write-Output-Of-For-Loop-To-txt-File

In Carl Love  's answer, I felt the power of adjacency matrix of graph. I carefully read maple's function to generate non IsomorphicGraphs:  NonIsomorphicGraphs. There was one passage that I thought was really interesting.

I never quite understood what the advantage of this bits was. At least according to the help documentation, we have  to do many works to do to convert this into a adjacency matrix of graph.

[NonIsomorphicGraphs(8, output = graphs, restrictto = regular[2])]

bit := Vector[row](Bits:-Split(210256131, bits = (8*(8 - 1))/2));
M := Matrix(8, 8, shape = symmetric, datatype = integer[1]);
M[1, 2 .. 8] := bit[1 .. 7];

M[2, 3 .. 8] := bit[8 .. 13];

M[3, 4 .. 8] := bit[14 .. 18];
M[4, 5 .. 8] := bit[19 .. 22];

M[5, 6 .. 8] := bit[23 .. 25];

M[6, 7 .. 8] := bit[26 .. 27];
M[7, 8 .. 8] := bit[28 .. 28];
M;

From adjacency matrix of graph,  we can diractly get a lot of information about the graph, like edges, and the number of closed walks of a particular length, but from bits , what imformation of graph we can get?

If we have to convert it to an adjacency matrix fist, maybe it's a little bit more complicated from above long codes. At least there isn't a more efficient way to convert?

Hi,

I am generating several random weighted graphs using the following code:

with(GraphTheory):
with(RandomGraphs):
G:=RandomGraph(10,20,connected):
G1:=AssignEdgeWeights(G,5..25):
DrawGraph(G1,showlabels=true,stylesheet=[edgecolor=blue,weightfont = [times,bold,11]])

By default weight labels appear to be positioned at the midpoint of each edge. Is there a way to change that positioning?

Thanks!

For example, given two zero-one n*n Matrices R and S. Find their transitivities (find [a,b] that satisfy R_a,x = 1 and S_x,b = 1)

How can I do this?

Dear All, If I understood well dsolve uses the RK45 method to solve an ODE. I would like to compare the results of tha attached worksheet with the results of another software that uses RK4 as a standard. Can I adapt my worksheet to use RK4 and how do you do that? Thanks in advance for your willingness to help me out.QMP_Nov21.mw

Hi ! 

I want to know how to ask Maple to transform a system of ODE in cartesian coordinates (e.g. [x'(t)=u(t) , u'(t)=-x(t)])

into a system in polar coordinates (in my example [r'(t)=0, theta'(t)=-1]). 

Many thanks!

Kevin

Hi,

I am trying to evaluate the diff of a function at a parametric point. But the outcome seems wrong in comparison with a case that we evaluate diff at a numeric point. 

Please observe the attached picture to get my problem.

Thanks in advance.

have table like table(symmetric, [() = x]) from other code not mine, strange syntax

how to extract x from table thanks

I have the following code. I want to do the modify it so that:

1. The outputs of each for loop are merged in such a way that the outputs from the first loop (Es) that are also outputs of the second loop (Fs) are removed from the outputs of (Es).

2. The resulting outputs G= .... are saved to a text file, one to each line.

3. In between each output, I want to add 5 lines of text and a blank line, say

text1 text2 text3

text2 text2 text3

text3 text3 text3

text4 text4 text4

text5 text5 text5

(blank line)

so that in the text file, the format is (e.g.)

G={{1,2}};

text1 text2 text3

text2 text2 text3

text3 text3 text3

text4 text4 text4

text5 text5 text5

(blank line)

G={{1,2},{1,3}};

text1 text2 text3

text2 text2 text3

text3 text3 text3

text4 text4 text4

text5 text5 text5

(blank line)

etc.

What is the easiest way to accomplish this?

restart;
 
with(GraphTheory):
 n:= 4:
  L:= NonIsomorphicGraphs
      ( n,
        output=iterator,
        outputform=graph):
  Es:= Array
       ( [ seq
           (  Edges( L() ),
              j=1..NonIsomorphicGraphs
                   ( n,
                     output=count
                   )
           )
         ]
       ):


  M:= NonIsomorphicGraphs
      ( n-1,
        output=iterator,
        outputform=graph):
  Fs:= Array
       ( [ seq
           (  Edges( M() ),
              j=1..NonIsomorphicGraphs
                   ( n-1,
                     output=count
                   )
           )
         ]
       ):
;

numelems(Es): 
for i from 1 to numelems(Es) do G:=Es[i]:  od;
                           
numelems(Fs):
for i to numelems(Fs) do G := Fs[i]; od;
                        

Hey everyone ! 

I want to get the analytical function from a piecewise differential equation defined on 6 intervals but Maple returns me a numerical result... I think it hides a Runge Kutta method.. However, it returned me an analytical function for a similar piecewise differential equation defined on 3 intervals.

Do you know how I could get the analytical function defined on the 6 intervals ?

Thank you very much for your time ! 

Alex

Download cas_5v_F_inconnues.mw

Download test.mw

Hey everyone!

I would like to plot the integral of a discrete function. For simplicity, I choose the function sin(x) between –Pi and Pi, which has as an integral -cos(x). I tried to implement that in Maple using the Trapezoidal rule, but the result is simply wrong. Any help would be much appreciated!

I have the following Maplesoft code:

with(ImageTools);

with(IterativeMaps):
Crystal, xrange, yrange := Attractor([x, y], [[1/2 - y/2, x/2], [y/2 + 1/2, 1/2 - x/2], [x/2 + 1/4, y/2 + 1/2]], height = 400, width = 400, xmin = -1, xmax = 2, ymin = -1, ymax = 1, fixview = true, [0, 0], [0.33, 0.33, 0.33], greenexpression = 1 - 1/(1/(1 - G) + 1), iterations = 2500000);
xrange, yrange;
                        -1 .. 2, -1 .. 1

ColouringProcedures:-HueToRGB(Crystal);
                               0.

Embed(Crystal);

which yields the following image:

However, I should be seeing the following image:

Any help would be appreciated. Thanks!

Justify that 2 vectors (1,1) and (1,2) are an R² base; How to write calculations correctly ?
<x, y> = lambda*<1, 1> + mu*<1, 2>:
 solve({lambda+mu=x,lambda+2*mu=y},{lambda,mu}):
 <x, y> := (2*x - y)*<1, 1> + (-x + y)*<1, 2>:
Thank you.

I get this error when I try to use the ODE numeric solver, can anybody help me figure out what Im doing wrong? 

hi guys,

I have a question about computing reimann tensor in general relativity.

suppose we have schwarzschidl metric: ds^2=-(1-2*m*(r^-1))*dt^2+(1-2*m*(r^-1))^(-1)*dr^2+r^2*dtheta^2+r^2*sin^2(theta)*dphi^2.

I want to caclulate R[alpha,beta,mu,nu]*R[~alpha,~beta,~mu,~nu] where R[alpha,beta,mu,nu] is covariant form of Reimann tensor and also R[~alpha,~beta,~mu,~nu] is the contravariant form of Riemann tensor. I also want to calculate same thing for weyl tensor. please guide me.

with best regards.