Re: Function calling another function that uses NSolve - can't get this
- To: mathgroup at smc.vnet.net
- Subject: [mg123665] Re: Function calling another function that uses NSolve - can't get this
- From: Bob Hanlon <hanlonr357 at gmail.com>
- Date: Thu, 15 Dec 2011 04:52:42 -0500 (EST)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
Clear[secondaltb, advantagesecondalttheoretic]
Since secondaltb is defined using numeric techniques it should be
restricted to numeric arguments. While this doesn't cause a problem in
this specific case, it will avoid problems if secondaltb is itself
used in a numeric technique.
Use ReplaceAll ( /. ) to return a value rather than a rule.
Use Module to avoid conflict with any global definitions for b.
Don't use machine precision numbers in computations for which you are
looking for higher precision.
secondaltb[KP_?NumericQ, Ps_?NumericQ, C_?NumericQ, M_?NumericQ] :=
Module[{b},
b /. NSolve[Sqrt[2*M]*b +
InverseCDF[NormalDistribution[0, 1], Ps]*
Sqrt[4*(InverseCDF[NormalDistribution[0, 1], Ps]^2) +
4*Sqrt[2*M]*b + 2027226163*^-9*M] ==
KP*C - 2*(InverseCDF[NormalDistribution[0, 1], Ps]^2),
b, WorkingPrecision -> 20][[1]]]
advantagesecondalttheoretic[b_] =
Simplify[(1/(2*Log[2])*(b^2)) + Log2[b] + Log2[Sqrt[2*Pi]]];
advantagesecondalttheoretic[secondaltb[2^64, 95/100, 2^(-5538/100), 2295]]
14.210260698587007244
This can also be done symbolically until the final conversion to a real number.
Clear[secondaltb2]
secondaltb2[KP_, Ps_, C_, M_] = Module[{b},
Simplify[b /. Solve[Sqrt[2*M]*b +
InverseCDF[NormalDistribution[0, 1], Ps]*
Sqrt[4*(InverseCDF[NormalDistribution[0, 1], Ps]^2) +
4*Sqrt[2*M]*b + 2027226163*^-9*M] ==
KP*C - 2*(InverseCDF[NormalDistribution[0, 1], Ps]^2),
b][[1]]]];
advantagesecondalttheoretic[secondaltb2[2^64, 95/100, 2^(-5538/100), 2295]]//
N[#, 20] &
14.210260698587007244
Bob Hanlon
On Wed, Dec 14, 2011 at 6:02 AM, jdm <james.d.mclaughlin at gmail.com> wrote:
> I was trying to convert a function (advantagesecondalttheoretic below)
> from another system to Mathematica. Probably because the function it in turn
> called used NSolve, I couldn't seem to get it to work while it called
> this function - it seemed that where secondaltb output {b->whatever
> value}, there was no way for advantagesecondalttheoretic to access
> this value. I ended up having to call the secondaltb function
> separately, and then manually input the result from it to a new
> version of advantagesecondalttheoretic - the one below:
>
> This is, naturally, not much help if I want to plot any graphs!
>
> Could someone please take a look at the below code and tell me how I
> can get advantagesecondalttheoretic to call secondaltb and use the
> value of b that results from it? Thanks!
>
> secondaltb[KP_, Ps_, C_, M_] :=
> NSolve[Sqrt[2*M]*b +
> InverseCDF[NormalDistribution[0, 1], Ps]*
> Sqrt[4*(InverseCDF[NormalDistribution[0, 1], Ps]^2) +
> 4*Sqrt[2*M]*b + 2.027226163*M] ==
> KP*C - 2*(InverseCDF[NormalDistribution[0, 1], Ps]^2), b,
> WorkingPrecision -> 20]
>
> lnscale = N[1/(2*Log[2]), 20]
>
> sb = secondaltb[2^64, 0.95, 2^(-55.38), 2295]
>
> {{b -> 3.8915440624385913563}}
>
> advantagesecondalttheoretic[b_] := (lnscale*(b^2)) + Log2[b] +
> Log2[Sqrt[2*Pi]]
>
> N[advantagesecondalttheoretic[3.8915440624385913563], 20]
>
> 14.210260698586953991
>
--
Bob Hanlon