Let L = {a1, a2, ..., an} (or L = [a1, a2, ..., an]) with is homogeneous polynomial. How to create function createDegree() return elements of degree <= n from L.

Expamle. L = {a-2b, b^2, (a+c)^2}.

createDegree(L,1) return {a - 2b}.

createDegree(L,2) return {b^2, (a - 2b)^2, (a+c)^2, a - 2b}.

createDegree(L,3) return {b^2, (a - 2b)^2, (a - 2b)^3, (a+c)^2, (a - 2b)b^2, (a - 2b)(a+c)^2, a - 2b}.

Thanks you very much.

Hello everyone!

Could somebody help me with reading data from Huge txt-file? My file contains matrix with 10 columns and 10^6 rows. Datatype is float[8].

I use "ImportMatrix" comand to obtain data from file, but it is rather slow ~ 33 sec.

is there an efficient way to read file directly using Maple? Or I should use C-dll to read file faster?

I want to calculate the ratio of the length of day and night for every latitude on earth ?
but i confused on using Maple in a wise way for finding the formula !
this is my demonstration :

shekofte000.mw
 

Download shekofte000.mw

As you see above, when I want to evaluate the definite integral, Maple can not provide the desired result. Why does this happen? How can I do so that Maple can calculate this integral?

Hello

Tryed to work this application, but problems encountered.

http://www.maplesoft.com/applications/view.aspx?SID=89020

and

http://www.mapleprimes.com/maplesoftblog/89021-The-Traveling-Salesmans-US-Roadtrip

I installed PostgreSQL, (i believe version 8.4 from 2010) which I found at "oldapps" (the current version is 9.6).

I'm running Win 7, 64 bit. Anyways, I have to change the paths below "Query the database":

driver := LoadDriver(classpath = "C://Program Files (x86)//PostgreSQL//pgJDBC//postgresql-8.4-701.jdbc4.jar");

conn := driver:-OpenConnection("jdbc:postgresql://localhost:5432/zip_codes", "postgres", "password");

I fail to see pgJDBC folder and a search for .jar files in the directory yields only 3 jar files, non resembling the above. tried example.jar

same error. heres a screenshot of my directory

Please i need help to plot the graph of f'' against episoln using the below BVP

HELP.mw

I want to plot the following equation

((1/2)*x*tan(log((1/5)*(2*(x^2+y^2)))) = y

I tried:

with(plots, implicitplot)

implicitplot((1/2)*x*tan(log((1/5)*(2*(x^2+y^2)))) = y, x = -5 .. 5, y =-5..5, numpoints = 1000, gridrefine = 6, color = red)

but result is strange... 

Hello, I have a function defined as

                                                   g :=  (x, y)->diff(u1(x, y), x, x)+diff(u2(x, y), x, y). 

I want to define another function as follows

                                                           f :=  (y) ->subs(x = 0, g(x, y)) ,

Now, when I want to calculate numerical values for the new function f(0), f(0.1), f(0.2),..... and so on. The following massage appear

Error, (in f) invalid input: diff received 0, which is not valid for its 2nd argument.

What is the problem here.

Amr
 

I'm curious to know if anyone has written a procedure to optimize the VRP with time windows / constraints.

I have a system of ode's

restart:with(plots):
eq1:=((diff(f(x),x$3)))+f(x)*diff(f(x),x$2)-a*diff(f(x),x$1)^2=0;
eq2:=(diff(g(x),x$2))+b*f(x)*diff(g(x),x$1)=0;
bc1:=f(0)=0,D(f)(0)=1,D(f)(5)=0,g(0)=0.5,g(5)=0;

dsolve can solve it easily.

sol:=dsolve(subs(a=0.5,b=0.5,{bc1,eq1,eq2}), numeric):

Now I was to use the numerical data from the sol in the following expression

Expr:=a*f(x)+b*g'(x)+c*f'(x)*g(x) # at x=1:

to make a table of this form a  b  c  Expr, where a, b, c vary simultaneously between 0 and 1 by 0.2 producing data for Expr.

Any suggestions? 

Hi everyone!

I have a question: what is the simpliest way to generate colorbar for spectrogram?

Now I use "valuesplit" to assign dependece "z"-value from color.

My programm. My test file: "Signal.txt".

filtered_spectrogram.mw

Signal.txt

P.S. I use Maple 2016.

Helle everybohy,

I need to setup a metric tensor in 3-d but with the varalble r, and .  So I try this:

>with(Physics); Setup(mathematicalnotation = true, dimension = 3)

>Setup(coordinates = spherical[r, theta, varphi], metric = M)

where M is the metric that I need to use.  But the last command does not work.  Il I don't write [r, theta, varphi], it work but it's r, theta and t.

Any hint on this please?

Thank you in advance for your help.

Mario Lemelin

mario.lemelin@cgocable.ca

all
I need your help  to give an answer to  this question
I would like to construct a matrix with condtion that comes in picture
How can i do this with maple????
my matrix is n+1*n+1

In this post I want to present an easy method to obtain a discrete parametrization of a surface S defined implicitly (f(x,y,z)=0).
This problem was discussed here several times, the most recent post is
http://www.mapleprimes.com/posts/207661-Isolation-Of-Sides-Of-The-Surface-On-The-Graph

S is supposed to be the boundary of a convex body having (x0,y0,z0) an interior point and contained in a ball of radius R centered at (x0,y0,z0).
Actually, the procedure also works if the body is only star-shaped with respect to the interior point, and it is also possible to plot only a part of the surface
inside a solid angle centered at (x0,y0,z0).

Usage:
Par3d(f, x=x0, y=y0, z=z0, R, m, n,  theta1 .. theta2,  phi1 .. phi2)

f           is an expression depending on the variables x, y, z
x0, y0, z0  are the coordinates of the interior point
R           is the radius of the ball which contains the surface,
m, n        are the numbers of the grid lines which will be generated
The last two parameters are optional and are used when only a part of S will be parametrized.

The procedure Par3d returns a MESH structure M, which can be plotted with PLOT3D(M).

Par3d :=proc(f,x::`=`,y::`=`,z::`=`,R,m,n,th:=0..2*Pi,ph:=0..Pi)
    local A,i,j, rij,fij,Cth,Sth,Cph,Sph, theta,phi, r;
    A:=Array(1..m+1,1..n+1,1..3,datatype=float[8]);
    for i from 0 to m do for j from 0 to n do
      theta:=op(1,th)+i/m*(op(2,th)-op(1,th));
      phi:=op(1,ph)+j/n*(op(2,ph)-op(1,ph));
      Cth:=evalf(cos(theta)); Sth:=evalf(sin(theta));
      Cph:=evalf(cos(phi));   Sph:=evalf(sin(phi));
      fij:= eval(f, [lhs(x)=rhs(x)+r*Sph*Cth, lhs(y)=rhs(y)+r*Sph*Sth, lhs(z)=rhs(z)+r*Cph]);
      rij:=fsolve(fij,r=0..R);  if [rij]::list(numeric) then rij:=min(rij) fi; 
      if [rij]=[] or not(type(rij,numeric)) then print(['i'=i,'j'=j], fij); rij:=undefined fi; 
      A[i+1,j+1,1]:=evalf(rhs(x)+rij*Sph*Cth);
      A[i+1,j+1,2]:=evalf(rhs(y)+rij*Sph*Sth);
      A[i+1,j+1,3]:=evalf(rhs(z)+rij*Cph);
    od;od:
    MESH(A);
end:

The procedure is not optimized, e.g.
- Cth, etc could be Vectors computed outside the loops
- Some small changes to use evalhf.

###### EXAMPLES ######

f1 := x^2+3*y^2+4*z^2 - x*y - 2*y*z - 10:
plots:-implicitplot3d(f1, x=-5..5, y=-5..5, z=-2..2);

M:=Par3d(f1, x=0,y=0,z=0,5,40,40):
PLOT3D(M);

f2 := x^4+y^4+z^4-1:
M:=Par3d(f2, x=0,y=0,z=0,5,40,40):
PLOT3D(M);

M:=Par3d(f2, x=0,y=0,z=0, 5,40,40, 0..Pi, 0 .. Pi/3): #Plot half of the top only
plots:-display(PLOT3D(M), scaling=constrained);

M:=Par3d(f2,      x=0,y=0,z=0, 5,30,30, 0..Pi, 0 .. Pi):
N:=Par3d(f2+0.01, x=0,y=0,z=0, 5,30,30, 0..Pi, 0 .. Pi):
plots:-display(PLOT3D(M), color=red):
plots:-display(PLOT3D(N), color=green):
plots:-display(%,%%, orientation=[-40,65,10]);

f3 := (x^2+y^2-1)^2+(z+sin(x*y+z))^4-120:
plots:-implicitplot3d(f3, x=-4..4,y=-4..4,z=-5..5, numpoints=10000);

Par3d(f3, x=0,y=0,z=0,5, 30,30):
PLOT3D(%);

Note.
The procedure could be used to plot locally around a point (x0,y0,z0)
One may use the spherical coordinates (theta0,phi0) and then call the procedure taking theta0-a .. theta0+a,  phi0-b, .. phi0+b  for the trailing parameters
The spherical coordonates can be computed using:

ThetaPhi :=proc(x,y,z, X,Y,Z)
    local r:=sqrt((X-x)^2+(Y-y)^2+(Z-z)^2);
    ['theta'=arctan(Y-y,X-x), 'phi'=arccos((Z-z)/r)]
end:

ThetaPhi(10,20,30, 11,21,28);evalf(%);

Hi all,

How to calculate this integral:

for k>0,m>0

Int(exp(-(1/2)*v/k)*v^3*exp((1/2)*v/m)*Ei(1, -(1000*I)*v+(1/2)*v/m), v = 0 .. infinity)

I'm  tried to take advantage of with(IntegrationTools) but I failed

and and I got a strange result ,like this:

Integral.mw