I am trying to adapt the code with Direct Search 2 for my needs but do not quite understand the syntaxis :( . I have system with 8 first order but nonlinear odes and 20 parameters but for starters I fix most of them (to estimate time consumption for full calculations etc). The part of the code where it ``breaks'' looks as follows:

#argument
X0:=Vector([24, 36, 48, 60, 72, 84], datatype = float):
#value
Y0:=Vector([13.8e+9, 12.13333333e+9, 10.7e+9, 10.5e+9, 9.8e+9, 10.1e+9], datatype = float):

#so this is the data - time in X0 and corresponding observables (at that time instances) at Y0

par_sol:=dsolve(dsys, numeric, range=0..85,  parameters=[eta_L, L0]);

#parametric numerical solution with eta_L parameter of the model and L0 initial condition to fit

ffit2 := proc(etaLValue, L0Value, tValue) global old_eta, old_L0; local res;
if not [etaLValue, L0Value,tValue]::list(numeric) then
      return 'procname'(args); end if;
if old_eta<>etaLValue and old_L0<>L0Value then
      (old_eta,old_L0) := etaLValue,L0Value;
      par_sol('parameters'=[eta_L=etaLValue,L0=L0Value]);
   end if;
   res:=rhs(par_sol(tValue)[4]); end proc;

# this is just adapted copy of your function

par_sol(parameters=[eta_L=0.004, L0=1.1e10]);

par_sol(84)[4];ffit2(0.004, 1.1e10, 84);

#their output coincide OK; same for another trio of parameters

DS2:=CodeTools:-Usage(
        DirectSearch:-DataFit(ffit2,X0,Y0,t,
                              [ eta_L=0.001 .. 0.1, L0=1.5e10 .. 1.7e10
 #                               
                              ] )
);

#and here it breaks:

Warning, initial point [L0Value = .9, tValue = .9] does not satisfy the inequality constraints; trying to find a feasible initial point
Error, (in DirectSearch:-Search) cannot find feasible initial point; specify a new one

But tValue is a time variable - I integrate over it, it is not a parameter to fit - I evaluate ffit2 at it. So basically ffit2 return exactly the model value which need to be fited with data in Y0 at times specified in X0. I thought it is easier than the other problems I saw in examples with Direct Search 2 and still I can't get through syntax neither with it not with NonlinearFit of core Maple...

I would appreciate if you could point me what I am doing wrong. Just in case I also attach full version of the file.01test.mw

Thank you in advance!

Hello. I want to organize some parameter
F=fsolve(1+x^2=j).

If j=-5, for example, an empty value 'F=' will be returned. How can I write the expression

If F=(void), then action 1, else action 2 end if

The fact is that I just don't know how to write the result (void), that is, the result of 'F ='

Thanks

Hi

I was wondering how one uses maple to solve for variables that comprise the limits of an integral?

X and R are between 0 and 1.

Any thoughts would be greatly appreciated, thanks in advance...!

Download Solvingforlimitsofintegrals.mw

When should i use ->  for a procedure definition and when not ?
In my post i do see examples of  procedures which are made on two different ways.
proc  ..end proc;

Still difficult to get a procedure on two ways 

test:=x->x^2;
Typesetting:-mprintslash([(test := x -> x^2)],[x -> x^2])

test(2);
4

restart;
test:= proc()
local x,a;
a:= x^2;
end ;
Typesetting:-mprintslash([(test := proc () local x, a; a := x^2; end proc)],[
proc () local x, a; a := x^2; end proc])

test(2);
x^2

test(3);
x^2

As you can see with the standard proc definition i getlost with  calculating x^2 

In the past I worked with mathcad where it was very easy to work with units. Now I try to switch to Maple but I am still struggling when I want to implement units. In the simple attached worksheet I try to multiply vector a in [m] with vector b in [cm]. I get an answer in [m] but I cannot convert the answer to another unit. Right clicking allows me to change the unit e.g. to mm but nothing happens in the worksheet. When I use convert, the units are expressed numerical in cm but the vector still shows m. My apologies in advance for this simple questions but I find no way to solve my issue.

CollabExample.mw

Anyone can help me to convert matlab codes to maple, pls, this is my code p

Can i make a natural numberline what shows the enumber of primes at each of 1000 numbers  
I have her

0-1000 : 168
1000 -2000: 135

2000-3000 : 127

3000- 4000: 120

4000 -5000 : 119 

then a gap (jump) 

10^7- 1000- 10^7  : 53 

You can see that the "number of primes"  is fluctuating
Can i make a procedure what calculates the latest mersenne prime number ?
Problem is only that there is a theorem: there are arbitrary long series of divisible numbers on the numberline 
There are gaps of length n - 1, where are no primenumbers  in positioned.

The idea is to get a idea of the distribution of primes to make a guess from where to start to find another one? 

Hello, I found this code from Acer works great:

p=floating point number such as 0.003483 

nprintf(`#mn(\"%1.3e\");` , p)

prints a number in Scientific format,    3.483e-03

Perfect.

HOWEVER, What is the #mn please?   Is it a comment, or a MathML function?

Regards, Bill

Dear all, do you know if there is a way to ask Maple and the Physics package to use the bold notation of vectors instead of using arrows? 

Thanks, Kevin

Hi,

I want to solve system of  PDE equations by maple and i dont know how can i write it codes that can solve them for me. Can anyone help me please??!!

Good day.

When I export an animated 3D (surface contour) plot to a gif format, the image is incomplete (please see attached file).

Can anyone suggest a way to reformulate the expressions so the animated plot can be exported to Powerpoint intact?

Thanks for reading!

MaplePrimes_Dec_5.mw 

Hi all !

I have a list of coupled ordinary differential equations 

L := [e1,e2,e3] = [diff(z(t), t, t)*m = 0, diff(x(t), t, t)*m - B*diff(y(t), t)*q = 0, diff(y(t), t, t)*m + B*diff(x(t), t)*q = 0] with unknown functions x(t),y(t),z(t).

I want to obtain the list of "normal forms" of the ode using the DEnormal function. The help page says that it is possible to use it with an operator list but none example is given. 

Thanks!

Kevin

December and Maple 2021.2 have both arrived, which means that we can look forward to year 2022 and Maple 2022.

        What should we like to find new in Maple 2022?  Here follow a few suggestions, to which readers of Maple Primes can add.

        In my opinion the weakest feature of Maple 2021 is the solution of integral equations.  Even when this package was first introduced into Maple, a couple of decades ago, it was weak, applicable to only linear such equations.  A quarter century earlier, David Stoutemyer (a true genius and entrepreneur, originator of Mu-Math, Mu-Lisp, Derive and computer-algebra capabilities incorporated in calculators of Texas Instruments) had published code for non-linear integral equations, based on Reduce.  There is a Handbook of Integral Equations by Polyanin and Manzhirov that lists about 2000 solutions of integral equations.  Let Maple 2022 be the basis of a boast by Maplesoft for Maple to be able to solve 96 per cent of those equations, in the same way that Edgardo Cheb-Terrab can (rightfully) boast that Maple can solve 96 per cent of differential equations in a standard compilation.  Any differential equation can, apparently, be converted to an integral equation, whereas the converse is not true.  For this reason alone, the development of solution of integral equations should become a priority to assist users of Maple.

        Another area worthy of expansion and enhancement is the solution of differential equations in terms of Heun functions; that capability is already present, but working with those functions in their present form is difficult and slow.  The inclusion of related functions, such as Lame functions, into Maple is long overdue.  Although efforts have been devoted to the development of the physics package in recent years, culminating in a tremendous achievement of capability, only a few physicists in the world can appreciate that luxury, whereas the solution of differential, and integral, equations permeates all science and engineering. 

          What items are on your list of wishes for Maple 2022?