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