brian bovril

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17 years, 326 days

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These are replies submitted by brian bovril

@acer But I get "server error" when I tried to download your second file 

@vv Thankyou. It works well. How did you derive your expression?

@acer Thankyou for your efforts. range 0.3<x<30, accuracy 3 digits.

The other thing to remember is excel won't accept a formula too long.

@acer Yes, I wanted to index into the names. Should I change the title?

@brian bovril with vv's help....

Turns out it wasnt a version issue. It took exception to something in my maple.ini file. Specifically it didn't like the declaration e:=exp(1);

@vv When I removed my maple.ini file, your code worked!

 it doesnt like my declaration  e:=exp(1);

print("maple init loaded...");

@vv I get errors when i run this code. M2018.0

@Carl Love Maple 2018.0

@Carl Love 

@acer Thanks. And Carl. I'm now trying to multiply the kWh/d by $0.27265/kWh to get 4.67 USD/d.

this didn't work 4.9*Unit(kW)*3.5*Unit(h/day)*0.27265*Unit(USD/kWh)

but this did....

restart:Units[AddSystem]( NewSI, Units[GetSystem](SI), USD/d );
 Units[UseSystem]( NewSI ); 
combine( 4.9*Unit(kW)*3.5*Unit(h/day)*0.27265*Unit(USD/kWh), units );

@Carl Love 

I would be interested to see your derivation of the formula.


A= the number of rats born in a liter
G= the "gestation" period that a newborn rat must wait before giving birth
I= the interval between births

If I supply G and I, i can get the series in terms of A, 

[NB the initial pair of rats produce A offspring immediatly]. 

restart:local I:
  sol3:=rsolve({U(n)=U(n-G/I+2)+A/2*U(n-G/I), U(0) = 2+A, U(1) = 2+2*A, U(2) = 2+3*A}, {U}, 'makeproc'):
  seq( sol3(j), j=0..5);

What I really wanted was a closed form solution of the populations as a function of day given the symbolic parameters A,G,I


thanks for your interest.

I tried this 

a:=unapply(rsolve({{U(n)=U(n-1)+3*U(n-3), U(0) = 6, U(1) = 6, U(2) = 6, U(3)=24}}, U(n)), n);  # General formula
seq(expand(a(n)), n=0..9);  # The first 10 terms

didnt work. Then I tried 

  sol1:=rsolve({U(n)=U(n-1)+3*U(n-3), U(0) = 6, U(1) = 6, U(2) = 6}, {U}, 'makeproc'):
  L:=[seq( sol1(j), j=0..9)];
 g:= gfun[guessgf](L,n, [ogf]); 

but, no cigar

@Joe Riel I found this in my Maple 7 folder. I suspect it was written by you.



1. I don't know where this is. I'm running M2017. I did right click in the help page "copy examples".

2. I don't think i am. I seem to remember it was a bugger to setup.


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