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Re: InverseFunction returning working function or just a symbol

• To: mathgroup at smc.vnet.net
• Subject: [mg126566] Re: InverseFunction returning working function or just a symbol
• From: LÃszlà SÃndor <sandorl at gmail.com>
• Date: Sat, 19 May 2012 05:46:36 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201205180923.FAA17055@smc.vnet.net> <4FB652E4.8010608@math.umass.edu>

Hi,
Sorry about this, I learnt this, but after I posted here already. I
posted the question on mathematica.SE too, with no confusing tags:
http://mathematica.stackexchange.com/questions/5691/inverse-function-not-working-but-providing-values-for-some-arguments-a-symbo

Thanks,

Laszlo

On Fri, May 18, 2012 at 9:47 AM, Murray Eisenberg <murray at math.umass.edu> wrote:
> Please don't include all the In[...] and Out[...] labels, because they make
> it hard to copy and paste executable code into Mathematica.
>
> On 5/18/12 5:23 AM, L=C3=A1szl=C3=B3 S=C3=A1ndor wrote:
>>
>> Hi all,
>> I am puzzled by the following behavior (focus on the end, the rest is only
>> to provide context):
>>
>> In[88]:= u[c_,l_]:=Log[c]-Log[1+l^(1+k)/(1+k)]
>> In[14]:= T[z_]:=(1-0.84/1.3) * z
>> In[103]:= umaxType[n_]:=MaxValue[{u[n l-T[n l],l],l>=0},l]
>> In[101]:= lType[n_]:=ArgMax[{u[n l-T[n l],l],l>=0},l]
>> In[105]:= zType[n_] := n lType[n]
>> In[111]:= Type := InverseFunction[zType]
>> In[134]:= Type[5345]
>> Out[134]= 5030.99
>> In[136]:= Type[2]
>> Out[136]= (zType^(-1))[2]
>> In[137]:= Type[4324424]
>> Out[137]= (zType^(-1))[4324424]
>>
>> I understand that there could be many justified reasons why the inversion
>> might not work for a specific argument. Still, I am deeply puzzled that
>> sometimes I receive back a symbol that nothing else is able to do anything
>> about (why not an error message, then?), sometimes a number. How could this
>> be improved?
>>
>> Thanks!
>>
>
> --
> Murray Eisenberg =C2  =C2  =C2  =C2  =C2  =C2  =C2  =C2  =
=C2  =C2  murray at math.umass.edu
> Mathematics & Statistics Dept.
> Lederle Graduate Research Tower =C2  =C2  =C2 phone 413 549-1020 (H=
)
> University of Massachusetts =C2  =C2  =C2  =C2  =C2  =C2  =C2=
  =C2 413 545-2859 (W)
> 710 North Pleasant Street =C2  =C2  =C2  =C2  =C2  =C2 fax =
=C2  413 545-1801
> Amherst, MA 01003-9305
>

• References:
  • InverseFunction returning working function or just a symbol
    • From: László Sándor <sandorl@gmail.com>