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machine precision number plot fixed in V6?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg83043] machine precision number plot fixed in V6?
  • From: congruentialuminaire at yahoo.com
  • Date: Thu, 8 Nov 2007 06:13:56 -0500 (EST)

Hello Mathematica UG:

I was doing some work with the PrecisionPlot package (http://
library.wolfram.com/infocenter/MathSource/715/)

When I ran it under V6, no output was emitted. So I looked again at
the documentation provided by Ted Ersek. Even though it is 8 years
old, it contains the following function and plot which does not work
correctly as recently as V5.

In V6, the invocation with SetPrecision works and emits a smooth plot
(presumably eliminating the need for this package). Here are the lines
of code.

-----------------------------------------------------------
(* a function that does not plot well with machine-precision numbers
*)
f2[x_] = ArcSec[x] - Normal[Series[TrigToExp[ArcSec[x]], {x, \
[Infinity], 7}]]

(* a jagged plot results under V5 and V6 *)
Plot[f2[t], {t, 25, 40}]

(* a smooth plot results only under V6 *)
Plot[f2[SetPrecision[t, 17]], {t, 25, 40}]
------------------------------------------------------------

If there is a simple explanation for what was fixed in V6 to make this
work, I am interested to know.

TIA.

Regards..Roger



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