I can't workout the syntax to plot a sequence of arrow. See last line of document.

accel := plottools:-arrow(seq([M[j, 1][1], M[j, 1][2]], [M[j, 3][1], M[j, 3][2]], j = 1 .. i), colour = red)  Doesn't work and tried various things.

Would also appreciate an explination for how the lines are plotted. I found this line on Maple Primes. It works but I don't realy understant it.

orb := plot(([seq])([M[j, 1][1], M[j, 1][2]], j = 1 .. i), colour = blue)

Why is seq in square brackets?

Download plot_arrows_sequence.mw
 

Download plot_arrows_sequence.mw

Dear sir, I hereby request you to suggest an appropriate method to plot phase portrait sketches for the above cited subject

in 2D and 3D for the problem  

With thanks and regards.

Mr M ANAND

Associate Profesoor in Mathematics.

This question is related to an answer I gave here:
So, please look at a simple worksheet containing only a few lines; the resuts are in the # comments.

restart;
evalf(frac(Pi^20));
#                              23.
restart;
printlevel:=40:
evalf(frac(Pi^20));
  ###  prinlevel stuff
#                              0.

And now the questions.
1. Why the first evalf(frac(Pi^20))  does not  call  `evalf/frac`?
     (the second does, trace(`evalf/frac`)  shows this  if inserted).
     Note that  `evalf/frac`(Pi^20)    returns  0.
2. Why evalf(frac(Pi^20))    depends on printlevel?
    Note that  if  printlevel is changed to 20 (say)  the result is again 23.
3. Why if we set interface(typesetting=standard)  in a fresh session
     the results are both 23?

I can't get a While do loop to work as expected.

For i from 2 while M[i,1]<>M[1,1] and i<25 do..   It doesn't catch row 15 where M[15,1] =M[1,1] but it does stop at i = 24 ok.
 

Download Test_While_do_loop.mw

Download What_is_New_after_Maple_2018.mw

Katherina von Bülow

Hello Friends

I have a critical problem that I wish to solve it with maple

suppose we have a list like following: y_obs=(2,4,8,7,9,52,35,478,52) and corresponding variance σy=(.2,.3,.5,.87,.1.2,.22,.78,.99,1.5)
we know y as the function of x described such as y_theoric=x+p and minimizing X is

X=Sigma [(y_theoric-y_obs)^2]/σy which includes the sum of nine numbers...

the question is:

How we can find p from likelihood function and plot general behavior of y versus of x through two above series?

for example this solution used in article under the names Hubble parameter data constraints on dark energy by Yun Chen and Bhatra Ratra (Physics Letters B)

Thank you

I mean 

restart;
 plots:-implicitplot(sqrt(b)*sqrt(1-4*p/b)-2*arctan(sqrt((9*p/b-22201/10000)/(9/4-9*p/b))) = 0, b = 0 .. 5,
 p = 0 .. 5, gridrefine = 2, rational);

I find the above result unsatisfactory.

Hello,

     I have a very large expression I'm tring to average (by doing limit(1/L*int(<expr>,t=-L..L),L=infinty) ). However, given that this expression is so large (sum of 11k terms), I'm was looking for ways to speed up the calculation and use less RAM.

     I found that applying the lim@int seperately to each term of the sum helps. Also, since my integrand has various functions of other variables (eg. f(x), g(y), etc), Maple seems to go faster if I freeze those functions using frontend.

     However, the problem I'm running into is that, as I'm running through my for-loop to apply lim@int to each term, Maple starts running slower and slower, as well as taking more and more RAM. Additionally, it doesn't go to completion because it runs out of stack space.

     Is there an optimization trick to avoid this problem? I've tried garbage collecting after each iteration; that helps the RAM problem (at a cost of speed), but it still slows down over time.

      I've attached my code: MWE.maple. Fair warning: on a non-server computer, it is liable to run very slow.

Is it possible to convert E1(x) to Ei(x) explicitly?

In particular I have this expression which is real, but imaginary numbers appear due to the definition of Ei1 for negative arguments.

(-exp(j*z)*Ei(1, j*z)+I*Pi*exp(-j*z)+exp(-j*z)*Ei(1, -j*z))/(2*j)

j>0,z>0

Thank you

The procedure F computes the smallest prime factor of  ithprime(n)-2

F := n -> ifactors((ithprime(n)-2))[2][1][1]:

F(11);
                               29
Strangely, print(F)  must be interrupted!
print(F);
Warning,  computation interrupted
 
Also,

F := n -> ifactors((ithprime(n)-2))[2][1][1];

Warning,  computation interrupted
Warning,  computation interrupted

(F is defined, only the display fails).
This happens only for interface(typesetting=extended).
In Maple 2017 it was OK.

how I can remove this error.

Error, numeric exception: division by zero

code2.mw

Hello,

      I was trying to apply some assumptions to a pdsolve command and noticed a strange error. Here's a minimal working example.

restart():

pdsolve(diff(f(t,x),t) = 0, {f(t,x)}, ivars = {x, t}) assuming x::real:

returns

Error, (in simpl/relopsum) invalid terms in sum: diff(f(t,x),t) = 0

Is this indeed a bug, or is it expected behavior?

We have released an update to Maple, Maple 2018.1. This release provides enhancements to the mathematical computation engine, including physics and DEs.  It also provides substantial improvements to the command line version, easier access to group management tools in the MapleCloud, and a few other interface improvements.

This update is available through Tools>Check for Updates in Maple, and is also available from our website on the Maple 2018.1 download page, where you can also find more details.

please see maple attachment below.

btw, what i'm really trying to do is represent spin 1/2 states, along with the usual spin operators, and be able to take tensor products of the spin states. any hints on how to do that would be greatly appreciated. 

btw, the physics package is amazing! 

thanks, 

larry

bug.mw

One of the frustrating things I am finding in using Maple debugger is that I can't set breakpoint using stopat() at some line number in some inner module, if the inner module is local module. It has to be an exported module.

Here is an example

restart;
foo:=module()
   export main_entry;
   local foo1; #inner module. But if local, Can't set breakpoint from outside

   foo1:=module()
     export main_entry;
     local foo2;

     foo2:=proc() #or breakpoint in first line here
        local s,x;
        s:=1;     #suppose I want to set break point here
        s:=s+sin(x);
     end proc;
     
     main_entry:=proc()         
        foo2();
     end proc;    
  end module;

  main_entry :=proc()
    foo1:-main_entry(); #call inner module's proc
  end proc;

end module;

Since there is inner module, local to outside module, I can't set break into the inner module procs anywhere.

stopat(foo:-foo1::foo2);
Error, module does not export `foo1`

A workaround for now is to change "local" to "export" on the inner modules declarations I want to debug, so I can setbreak points inside them, then when done, make them local again. So changed "local foo1" to "export foo1" above, and now

          stopat(foo:-foo1::foo2,2);

works.

This was also a little strange to me, since foo2() is a LOCAL proc to module foo1, yet Maple did not complain like it did when module foo1 was a LOCAL module to foo. I would have expected Maple to complain again for same reason.

So I am using the above workaround for now. But it is just a little annoying becuase I have to keep changing module from LOCAL to EXPORT in order to set breakpoints, then remember to make them local again.

Is there a better workaround?

A product suggestion: make stopat() ignore the local module setting and treat it as export for the purpose of setting a break point. This way one does not have to change the code just to set a breakpoint. Or if not to change current behavior, add a new option, as in

          stopat(........, option= ignore_local_setting)

So the default remain the same as now, but with the new option, it will set breakpoint anywhere, even in local modules.

Thank you