awass

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14 years, 318 days

MaplePrimes Activity


These are replies submitted by awass

@Preben Alsholm Hi,

Thankk you for your response.

I checked kernelopts(floatPi); in both Maple 2019 and 2020 and got true in both cases.

However, I realized from your answer that I got the wrong answer when Digits was set to 10 but if I put Digits:=15 all was well. I guess I was seeing round off error.

@Carl Love  That is quite subtle. Good to know. Thank you. I guess the longer displayprecision

is the command I will have to use.

@acer 

Thank you for explaining my error. As Tom Leslie also pointed out using evalf( ....,5) was my problem.


From the syntax-it sure looks like a composition- I assumed that since  f(g(x)) is computed by first computing g(x) then applying f to that result evalf( eval([W,Wp],nans(1.5)),5) would be computed by first evaluating eval([W,Wp],nans(1.5)), then applying evalf..., 5) to that answer.

In my work I was using dsolve with Digits:=35 and error tolerances of 10 ^(-14). I guess evalf overrides those instructions somehow. So be it.

 

The interface setting does resolve my issue.

@tomleslie 

 

I do not see any major changes you have made. Could you please explain? I also do not understand what you dislike about my code or where it might go wrong. f'^2 cos(x) /f^2 > 0 for any any f if 0 < x < πi/2.

@Carl Love evalf_error.pdf

 

does this help?

@Earl  I am hoping that the full set of rules for using events will appear-perhaps inMaple 2021-and will answer all my questions. Meanwhile, it is useful to see your apllication of the command.

@Preben Alsholm 

Thanks.

So I am not the only one who finds the Help pages opaque.

BTW, I still rely on an answer you suplplied 9?15/17 to use events. I am hoping to be able to use the commands more comfortably in Maple 2021.
 

@Kitonum I just have to remember it. Wouldn't it be nice if it was one of the examples on the Help page?

@acer 
Thank you for clarifying the syntax.
I am familiar with the archaic usuage of the dot to denote concatenation but that was not my intent; I was merely eliminating spaces and hoping that would be more acceptable to Maple.

@acer 

Thanks for your help. The 2D supresses y(x) but not dy(x)/dx.

@Thomas Richard 

Many thanks for help with my mini-issue. I now have a working file.  Hooray!

@nm.   lists are not mutable, Vectors and Matrices are. For big projects that can make quite a difference.
 

The suggestion (by acer or Joe Riel) to make a copy of the structure is just what is needed.

@acer 

Strange that the compact option is cancelled implicitly when you multiply by 2.


Thanks for the explanation and also for the pointer to Section 6.7 of the Programming Manual which is quite helpful.

@acer Thank you for your explanation. I guess the copy command is just necessary for vectors and matrices; it is not necessary for lists or scalars.

I thought I understood until I tried to apply my new "knowledge" in a slightly different context.
 

I wanted to construct a matrix by altering the identity matrix a bit.  Putting A:=IdentityMatrix(5); A[2,3]:=7; resulted in an error message. You explained why above so..

A:=copy(IdentityMatrix(5)); should work. Nope.

A[2,3]:=7; still resulted in an error message.
My very silly workaround:
B:=2 IdentityMatrix(5); B[2,3]:=14; A:= 1/2 B;
There must be a better way.

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