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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: RE: RE: truncating graph range |

Date |
Mon, 31 Oct 2005 11:19:32 -0000 |

Allan's main advice is to fit a regression line with an outlier and to show it on a graph together with all the other data. That's often a useful technique, but I read Timothy's discussion of line plots as wanting something quite different, namely * outlier off graph / \ / \ / \ lines on graph pointing to it I am sure that this is programmable, but I don't know an easy and general way for a user to do it. Likewise Allan's other suggestions do not seem to bear on this problem. Nick n.j.cox@durham.ac.uk Allan Reese (Cefas) > Hate to disagree with Nick, but Stata is well-designed for > intelligent graph editing. Timothy maybe needs to fiddle > with a few alternatives and work out what would show what he > intends. A log scale is one option but has many other implications. > > For example, it's straightforward in Stata to draw lines > with/without outliers. Other "point'n'click" packages don't > make this easy, so suppress the desire. > > fit y x > predict yhat1 > fit y x if y<1000 > predict yhat2 > scatter y yhat1 yhat2 x if y<1000, connect(. l l) msym(o i i) sort > > Another simple trick is to copy one variable into several, so > subsets can be distinguished on the plot. You could automate > this (eg, using egen to save the max value of x), but I'd > usually do it as part of visual editing, for example to add > text labels to the points at the end of each line. It's > therefore feasible to draw a line for the data excluding the > outlier, and add a second line in different style pointing up > with a label at its end describing the outlier. > > This is the type of work where I'd draft commands in a DO > file so they are easily modified and re-run. Nick Cox > What you want is _not_ straightforward. I know no easy and also > general way of omitting a data point from a Stata graph and also > having it exert some offstage influence on the remainder of > the graph. > > In my experience, when people think they want something like > this using a logarithmic scale for the variable concerned is > usually the > best way forward. Timothy Dang > > I'm making a lot of (line) plots in Stata, and mostly it's working > > great, but I've hit a snag. For a few of my data sets, > there are some > > data points which are extraordinarily high. With the automatically > > scaled axis ranges, these points are visible, but all the detail of > > the rest of the data is shrunk to invisibility. > > > > So, I want to: > > (a) enforce a maximum for the axis, hopefully showing the > lines going > > up towards some point not shown on the plot, and > > (b) add some text describing what happens at those points (I can do > > this outside Stata if needed). > > > > Hopefully this is straightforward and I've just missed something. > > Thanks for any pointers. * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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