AndreaAlp

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6 years, 107 days
University of Verona

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These are questions asked by AndreaAlp

Dear bright people of MaplePrimes, 

I'm stuck in a problem with dsolve.

I have a ODE system that I would like to solve numerically (because it's huge) in vars: var1(t), var2(t), var3(t), etc... Inside the ODE there are procedures with arguments like proc(f(x,y), a, b, c, etc...) where f(x,y) is a function for a curve (so x and y are variables) and a,b,c are numeric. 
Procedures have been written as indicated in the help page, i.e. differentiating whether the procedures are called with symbolic arguments or numeric arguments. So I call dsolve specifying the "known" procedures and a numeric method. Maple sets the problem correctly. However, when it tries to solve the equations numerically it points out that in the ODE ys there are some undefined parameters. Specifically, those parameters are x, y. But, again, x and y are not parameters but variables that are used in the procedures within the ODEs. 

I tried to include x and y as parameters and solve the system. However, before retrieving the solution, a numerical value must be given to all the parameters. 

What should I do if I need to keep f(x,y) symbolic in my procedures but I want to solve my ODE numerically? 

Thank you for supporting me. 
Thank you so much. 

Andrea



 

 

Hello everyone, 

please need some brain power here to help me with this problem. I'm stacked here and I cannot find a solution. 

I would like to find the intersection between a plane and a quadric surfaces. Please notice that the two equations are written like f(x,y) and g(x,z) respectively. My first problem is that I cannot visualize the two surfaces correctly as implicitplot3d of the quadric surfaces displays nothing in return. 

I want then to find the centre of the ellipse and plot the point and the two surfaces all together in the same 3d plot. Somehow I canont make it. What is wrong with me? 

I am pasting here my MWE. 

Any kind of help would be really appreciated. Thank you so much. 

Andrea

MWE_maple_help.mw
 

restart:

with(plottools):
with(plots):

with(Student:-MultivariateCalculus):
with(Student:-Precalculus):
with(geometry):

with( Optimization ):

my_plane := 2024.30587449691-.341275505799078*x-3.89936179341114*y;
my_quadric := -10595.4104931095+6.73749956241827*x+42.1022818380012*z-0.654818649508000e-1*x^2-0.421174257681115e-1*z^2;

2024.30587449691-.341275505799078*x-3.89936179341114*y

 

-10595.4104931095+6.73749956241827*x+42.1022818380012*z-0.654818649508000e-1*x^2-0.421174257681115e-1*z^2

(1)

my_quadric_plot_3d := implicitplot3d(my_quadric, x=-10000..10000,
                                       y = -100..100,
                                      z=-10000..10000,color="DodgerBlue"):
my_plane_plot_3d := implicitplot3d(my_plane, x=-10000..10000,
                                       y = -100..100,
                                      z=-10000..10000,color="DarkOrange"):

my_ellipse := CompleteSquare( subs(y = solve(z = my_plane, y), my_quadric));

-0.4211742577e-1*(z-499.8202178)^2-0.6548186495e-1*(x-51.44553815)^2+99.68250

(2)

ellipse(e1, my_ellipse, [x,z]):
XY_centre_e1     := coordinates(center(o,e1)):
my_center_point := [XY_centre_e1[1],XY_centre_e1[2],
                       subs(x=XY_centre_e1[1], y=XY_centre_e1[2], my_plane)]:
my_center_point_plot := pointplot3d(my_center_point, color = "red"):

display(my_center_point_plot, my_plane_plot_3d, my_quadric_plot_3d);

 


 

Download MWE_maple_help.mw

 

 

Dear all

i am writing some differential equations with Maple. I'd like now to generate the Matlab code and let them run. Unfortunately I need the closed form but Maple does not distinguish (at first sight, of course) between time functions and parameters. But what in Maple is a time function, will be an array in Matlab. Unfortunately in Matlab environment the array product is carried out by the meaning of the element-by-element command: ".* " .

Using CodeGeneration[Matlab...

Further tags : implicit form, Matlab codegen for GPOPS purposes

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