Re: Plotting f = Function[x,expr] and f[x_] := expr

*To*: mathgroup at smc.vnet.net*Subject*: [mg92451] Re: Plotting f = Function[x,expr] and f[x_] := expr*From*: "Jean-Marc Gulliet" <jeanmarc.gulliet at gmail.com>*Date*: Tue, 30 Sep 2008 21:55:23 -0400 (EDT)*References*: <gbt2oo$lbo$1@smc.vnet.net> <48E22E69.7060700@gmail.com>

On Tue, Sep 30, 2008 at 4:45 PM, E. Martin-Serrano <eMartinSerrano at telefonica.net> wrote: > Hi, > > This corresponds to the run in my version 6.0.1. Perhaps the source of the > problem is a bug in this version. This happens to occur with David Park's > Presentations package too. > > In[1]:= f[x_] := -20 x^3 + 3 x^5 > In[2]:= g = Function[x, -20 x^3 + 3 x^5] > Out[2]= Function[x, -20 x^3 + 3 x^5] > In[3]:= Function[x, -20 x^3 + 3 x^5] > > Out[3]= Function[x, -20 x^3 + 3 x^5] > In[4]:= Plot[g''[x], {x, -2 Pi, 2 Pi}, PlotStyle -> Blue] === > Plot[f''[x], {x, -2 Pi, 2 Pi}, PlotStyle -> Blue] > > Out[4]= False > In[5]:= $Version > Out[5]= "6.0 for Microsoft Windows (32-bit) (June 19, 2007)" Yes, it seems to be platform dependent. In[1]:= f[x_] := -20 x^3 + 3 x^5 g = Function[x, -20 x^3 + 3 x^5]; Plot[g''[x], {x, -2 Pi, 2 Pi}, PlotStyle -> Blue] === Plot[f''[x], {x, -2 Pi, 2 Pi}, PlotStyle -> Blue] $Version Out[3]= True Out[4]= "6.0 for Mac OS X x86 (64-bit) (May 21, 2008)" Regards, -- Jean-Marc P.S. I have sent by private email a PDF file showing the evaluation of the code below. > -----Original Message----- > From: Jean-Marc Gulliet [mailto:jeanmarc.gulliet at gmail.com] > Sent: martes, 30 de septiembre de 2008 14:49 > To: E. Martin-Serrano; mathgroup at smc.vnet.net > Subject: Re: Plotting f = Function[x,expr] and f[x_] := expr > > E. Martin-Serrano wrote: >> Hi, >> >> Why this apparent estrange behavior while plotting functions under the >> formats f[x_] := -20 x^3 + 3 x^5 and f = Function[x, -20 x^3 + 3 x^5]?, >> >> In particular the second derivative f ''[x] for -20 x^3 + 3 x^5 fails to >> render the shame shape in following examples . Please, see below: > > FWIW, to me as well as for Mathematica 6.0.3 on 64-bit Intal Mac OS X > 10.5.5, the plots are identical in each case. > > In[123]:= > > Clear[f, x] > f[x_] := -20 x^3 + 3 x^5 > pp1 = Plot[f[x], {x, -2 Pi, 2 Pi}, PlotStyle -> Red] > pp2 = Plot[f'[x], {x, -2 Pi, 2 Pi}, PlotStyle -> Green] > pp3 = Plot[f''[x], {x, -2 Pi, 2 Pi}, PlotStyle -> Blue] > pp4 = Plot[{f[x], f'[x], f''[x]}, {x, -2 Pi, 2 Pi}, > PlotStyle -> {Red, Green, Blue}, > PlotRange -> {{-6.28318, 6.27681}, {-14129, 14084}}] > > Clear[f, x] > f = Function[x, -20 x^3 + 3 x^5]; > p1 = Plot[f[x], {x, -2 Pi, 2 Pi}, PlotStyle -> Red] > p2 = Plot[f'[x], {x, -2 Pi, 2 Pi}, PlotStyle -> Green] > p3 = Plot[f''[x], {x, -2 Pi, 2 Pi}, PlotStyle -> Blue] > p4 = Plot[{f[x], f'[x], f''[x]}, {x, -2 Pi, 2 Pi}, > PlotStyle -> {Red, Green, Blue}, > PlotRange -> {{-6.28318, 6.27681}, {-14129, 14084}}] > > p1 === pp1 > p2 === pp2 > p3 === pp3 > p4 === pp4 > > > Out[135]= True > > Out[136]= True > > Out[137]= True > > Out[138]= True > > In[139]:= $Version > > Out[139]= "6.0 for Mac OS X x86 (64-bit) (May 21, 2008)" > > Regards, > -- Jean-Marc > > -- Jean-Marc