Re: Re: Putting an If in my function

*To*: mathgroup at smc.vnet.net*Subject*: [mg101093] Re: [mg101073] Re: Putting an If in my function*From*: Porscha Louise McRobbie <pmcrobbi at umich.edu>*Date*: Wed, 24 Jun 2009 06:29:07 -0400 (EDT)*References*: <h1neun$8rk$1@smc.vnet.net>

Hi, I'm also interested in adding a special case to a function. Using what's written below works fine: myFun[a_, g_, f_, x_, d_, w_] := d + a f x /; g == w But why doesn't the same work when the myFun is defined using "=" instead of":="? i.e., myFun[a_, g_, f_, x_, d_, w_] = (d + a f x) /; g == w ln[5]:=myFun[a, w, f, x, d, w] Out[5]=d + a f x /; w == w Thanks, Porscha Quoting "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>: > Dear lobotomy, > > "Nomen est omen", the old Romans used to say. And they were often > right. > > I'm not sure what you are trying to do here, with your function in an > unneccessary, overly complex, pure function notation. Why not write: > > myFun[a_, g_, f_, x_, d_, w_] := d (1 + (E^g - E^w)/f)^(f x) + (a (-1 > + (1 + (E^g - E^w)/f)^(f x)) f)/( E^g - E^w) > > which is much more readable (at least in Mathematica)? > > In[31]:= Limit[myFun[a, g, f, x, d, w], g -> w] > > Out[31]= d + a f x > > You use the undefined 'n' in d + a n. I guess this must be f x... > > You can add a definition for myFun for this special case like this (no > If[ ] necessary): > > myFun[a_, g_, f_, x_, d_, w_] := d + a f x /; g == w > > In[36]:= myFun[a, w, f, x, d, w] > > Out[36]= d + a f x > > If you want to use an If in the definition this would be something > like: > > myFun[a_, g_, f_, x_, d_, w_] := If[g===w, d (1 + (E^g - E^w)/f)^(= f= > x) > + (a (-1 + (1 + (E^g - E^w)/f)^(f x)) f)/( E^g - E^w),d + a f x] > > Cheers -- Sjoerd > > On Jun 22, 10:21 am, Lobotomy <labb... at gmail.com> wrote: >> Hi, this is my function >> >> #5 (1 + ((E^#2 - 1) - (E^#6 - >> 1))/#3)^(#3*#4) + (#1*((1 + (((E^#2 - 1) - (E^#6 = > - >> 1))/#3))^(#3*#4) - >> 1))/(((E^#2 - 1) - (E^#6 - 1))/#3) &[a, g, f, x, d, w] >> >> in the case when w==g the denominator equals zero. >> >> in this case i would like to rewrite the formula above to the much >> simpler >> d+a*n. How is this done? I've tried >> >> If[w == g, % = d + a*n], but this is not working. Another thing is >> where to put the "If" > > > > >

**Follow-Ups**:**Re: Re: Re: Putting an If in my function***From:*DrMajorBob <btreat1@austin.rr.com>