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Re: Mathematica 6 and normal distribution?

• To: mathgroup at smc.vnet.net
• Subject: [mg77961] Re: Mathematica 6 and normal distribution?
• From: sean_incali <sean_incali at yahoo.com>
• Date: Wed, 20 Jun 2007 05:42:23 -0400 (EDT)
• References: <f532e5$33l$1@smc.vnet.net>

I got the following email from Daniel Lichtblau of Wolfram in response
to my post.  I figured it will be useful for everyone.

> Has Mathematica 6 fixed the problems discussed in this thread?
>
>
http://groups.google.com/group/comp.soft-sys.math.mathematica/browse_frm/thread/f3d8f7cf40057943/350a024cc20c290b?lnk=gst&q=normal+distribution&rnum=2&hl=en#350a024cc20c290b
>
>>From their website it seems like they are saying NormalDistribution
is
> new in Mathematica 6.
>
> Has anyone run the codes to check?  Last time the problem was in the
> 25th bin in the code below--with the value at 25th bin being lower
> than the rest.
>
> SeedRandom[1111111 ];
> vec1=Table[Random[Real,{0,1000}],{10^6}];
> vec2=Map[If[#<44,1,0]&,vec1];
> ones=Flatten[Position[vec2,1]];
> plotvec=Map[Length,Split[Sort[Drop[ones-RotateRight[ones,1],1]]]];
> ListPlot[Log[plotvec],PlotRange->All]
> ListPlot[plotvec,PlotRange->All]
>
>
> Thanks for checking.
>

Random[] still exists for legacy purposes, and uses the same sometimes
problematic generators. If you use

vec1=RandomReal[{0,1000},{10^6}];

then the problem goes away in version 6.

Daniel Lichtblau
Wolfram Research