Mathematica 9 is now available
Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2007
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2007

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Self-teaching snag

  • To: mathgroup at smc.vnet.net
  • Subject: [mg74579] Re: [mg74556] Self-teaching snag
  • From: gardyloo <gardyloo at mail.wsu.edu>
  • Date: Tue, 27 Mar 2007 03:58:44 -0500 (EST)
  • References: <200703260704.CAA11373@smc.vnet.net>

Hi, Todd,

    charge[day_] := charge[day] = (charge[day - 1] - (0.05*charge[day - 1]));

That little change will make Mathematica remember its earlier
calculations in the recursion, so it won't spend all its time nesting a
bunch of charge[charge[charge[charge[....  ] ] ] ] expressions. I think
that was what was leading to the recursion error.

             C.O.


Todd Allen wrote:
> Hi All,
>
>    I am trying to refresh my skills in basic problem
> solving using Mathematica, but am running into some
> difficulties which are beginning to make me suspicious
> of Mathematica itself.  (I probably should be
> suspicious of my own brain...but you know how that is
> :-)
>
> Here is the scenario:  I have written a basic function
> to tell me what percentage of battery power will
> remain in a battery after x number of days, provided
> that we start with a full charge and lose 5% of that
> charge per day.
>
> If you execute the following code in Mathematica
> (V5.1):
>
> charge[0]=1.0 (* 100% *);
> charge[day_]:=(charge[day-1]-(0.05*charge[day-1]));
> charge[20]
>
> I receive an output of 0.358486 for my query at the 20
> day mark.....so, no problem so far.
>
> However, when I try to ask for the output at
> charge[35], mathematica seems to enter an endless
> calculation.  I've let the computer run for as long as
> 5 minutes without getting an answer.  Is there
> something wrong with my function, my version of
> Mathematica or something else I haven't considered?
>
>
> Additionally,
>
> When I try the following:
>
> In[145]:=
> Solve[charge[day]==0.15,day];
>
> Mathematica gives me the error:
> "$RecursionLimit::reclim: Recursion depth of 256
> exceeded."
>
> I am trying to ask Mathematica to tell my how many
> days it takes to reduce the battery power to 15
> percent, but I must be messing something up??
>
> If anyone has any pointers, I'd certainly appreciate
> it, because I am a little stuck right now.
>
> Best regards,
> Todd Allen
>
>
>  
> ____________________________________________________________________________________
> We won't tell. Get more on shows you hate to love 
> (and love to hate): Yahoo! TV's Guilty Pleasures list.
> http://tv.yahoo.com/collections/265 
>
>
>   


-- 
==========================================================
Curtis Osterhoudt
gardyloo at mail.remove_this.wsu.and_this.edu
PGP Key ID: 0x088E6D7A
Please avoid sending me Word or PowerPoint attachments
See http://www.gnu.org/philosophy/no-word-attachments.html
==========================================================



  • Prev by Date: Re: Self-teaching snag
  • Next by Date: Re: Self-teaching snag
  • Previous by thread: Re: Self-teaching snag
  • Next by thread: Re: Self-teaching snag