Re: question about the inverse li function
- To: mathgroup at smc.vnet.net
- Subject: [mg65374] Re: [mg65348] question about the inverse li function
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Wed, 29 Mar 2006 06:34:13 -0500 (EST)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
invLogInteg[y_?NumericQ]:=
x/.FindRoot[y==LogIntegral[x],
{x,y,y+2}][[1]];
Plot[invLogInteg[y],{y,-1,6},
PlotRange->{{-1.1,6.1},{-0.4,10.2}}];
For comparison,
Show[Plot[LogIntegral[x],{x,0,10},
DisplayFunction->Identity]/.
{x_,y_}->{y,x},
PlotRange->{{-1.1,6.1},{-0.4,10.2}},
DisplayFunction->$DisplayFunction];
Symbolically,
Off[InverseFunction::ifun];
Solve[y==LogIntegral[x],x]
{{x -> InverseFunction[LogIntegral, 1, 1][y]}}
InverseFunction[LogIntegral,1,1][LogIntegral[x]]
x
LogIntegral[InverseFunction[LogIntegral,1,1][x]]
x
Bob Hanlon
>
> From: "Capet Arthur" <Arthur.Capet at student.ulg.ac.be>
To: mathgroup at smc.vnet.net
> Subject: [mg65374] [mg65348] question about the inverse li function
>
> the question...
>
> i've measured C(x), wich is equal to li(I(x)), where li denotes the
> logarithmic integral function. I would like to compute I(x)= li^(-1)
> (C(x))
>
> how can i compute the inverse of the logarithmic integral function ?
> Is there a function Inverse[_function] ?
>
> thanx a lot
>
>
> Arthur Capet, ULG, Belgium
>
>
>
>