Re: Mathematica 4.2 & Strange Plot results
- To: mathgroup at smc.vnet.net
- Subject: [mg36316] Re: [mg36292] Mathematica 4.2 & Strange Plot results
- From: Dale Horton <daleh at wolfram.com>
- Date: Sat, 31 Aug 2002 01:26:00 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
At 12:19 AM 8/30/2002, Ken Thomson wrote: >I would expect that > >Plot[Sin[x]/Sin[x], {x, -2.5, -1.5}] > >would produce a horizontal line at y=1. > >However, on my Windows XP computer it produces a graph where the y value is >less than 1 at several points. Most notibly between x=-1.6 and x=-1.8 > >Is this just an isolated case? Or does it happen to others? If so - why? > >Regards, >Ken. The y axis has a very narrow range. The differences are very small. To see that, you can pull out the tick marks. In[13]:= yticks=FullOptions[gr,Ticks][[2]] In[15]:= InputForm[First/@yticks] Out[15]//InputForm= {0.9999999999999981, 0.9999999999999991, 1., 1.000000000000001, 1.000000000000002, 0.9999999999999983, 0.9999999999999986, 0.9999999999999987, 0.9999999999999989, 0.9999999999999993, 0.9999999999999996, 0.9999999999999997, 0.9999999999999999, 1.0000000000000002, 1.0000000000000004, 1.0000000000000007, 1.0000000000000009, 1.0000000000000013, 1.0000000000000016, 1.0000000000000018, 1.000000000000002, 0.9999999999999979, 0.9999999999999977, 1.0000000000000022} The ragged shape is caused by roundoff error, if you increase the PlotRange of the y-axis you see what you expect. gr = Plot[Sin[x]/Sin[x], {x, -2.5, -1.5}, PlotRange -> {0, 2}] -Dale