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
>
>
>
> ____________________________________________________________________________________
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>
>
--
==========================================================
Curtis Osterhoudt
gardyloo at mail.remove_this.wsu.and_this.edu
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==========================================================
- References:
- Self-teaching snag
- From: Todd Allen <genesplicer28@yahoo.com>
- Self-teaching snag