On Jan 20, 4:27 am, Daniel Harris <mail.dhar...@googlemail.com> wrote: > On Wed, Jan 19, 2011 at 1:33 AM, kcrisman <kcris...@gmail.com> wrote: > > > On Jan 18, 6:07 pm, Daniel Harris <mail.dhar...@googlemail.com> wrote: > >> On Tue, Jan 18, 2011 at 10:51 PM, Robert Bradshaw > > >> <rober...@math.washington.edu> wrote: > >> > On Tue, Jan 18, 2011 at 2:35 PM, Daniel Harris > >> > <mail.dhar...@googlemail.com> wrote: > >> >> Hello everybody > > >> >> I am just looking at sketching graphs and I came across a problem that > >> >> has me stumped. The graph I am trying to sketch is > > >> >> (x-3) / ( (x+1) * (x-2) ) > > >> >> now I have plotted the graph in sage on my TI-83 and at wolfram and > >> >> they all different. Now I am thinking is sage right and the others > >> >> wrong? or have I made an error inputting the equation? > > >> >> I would certainly welcome some help on the issue > > >> > What range are you plotting over? -1 < x < 1? -5 < x < 5? This could > >> > make a big difference on what the graph looks like. Likewise, what is > >> > the scale of the y-axis? I don't think Sage yet tries to remove the > >> > asymptotes at -1 and 2 from the plot. > > >> -1.5 < x < 3 the y peak at x=2 is the part that bothers me. It > >> doesnt seem to show up on my calc or wolfram alpha? > > > This is really showing the asymptote. If you do > > > sage: plot((x-3) / ( (x+1) * (x-2) ) ,(x,-1.5,3)) > > > sage: plot((x-3) / ( (x+1) * (x-2) ) ,(x,-1.5,3),ymin=-10,ymax=10) > > > you'll see what I mean. Unfortunately we don't have any 'guessing' > > for the vertical range. That's a bug and a feature at the same > > time :) A graphing calculator likely just picks something arbitrary > > for that. > > I think I understand now. What was confusing me was when I was > looking at a larger scale -30 < x < 30 the peak at x=2 was around 50 > but when I kept zoomin in the peak was getting larger, but now I know > now that is the asymptote. I guess that is why I need to be able to > sketch the graph and not to rely on a computer : ) >
:) But that doesn't mean it isn't worth Sage being able to 'intelligently' deal with such situations, and there are some tickets for this. You may also want to look at the documentation plot? to see about some asymptote/pole avoiding stuff (at least for visual presentation). - kcrisman -- To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
