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From |
"Eric G. Wruck" <ewruck@econalytics.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Additional lines on histogram |

Date |
Fri, 18 Nov 2005 11:27:53 -0500 |

Very nice -- thank you! Eric >Eric G. Wruck <ewruck@econalytics.com> asks, > >> I am generating a histogram but want to superimpose additional lines >> for certain values on the x-axis. However, the additional line is >> basically hidden behind one of the histogram bars, only appearing >> from the top of the bar to the top of the graph. Is there a way to >> bring the additional line to the top so that it is drawn on top of >> the histogram? > >I assume that Eric is using the -xline()- option to specify his vertical >lines. If so, those lines are "laid down" before the histogram bars are drawn >and are therefore occluded by the bars. In many (most?) cases this is what >you want -- your plots placed atop the vertical (or horizontal reference >lines). > >The position of the -xlines()- cannot be changed, but not to worry. >-histogram- supports the -addplot()- option, so we can add any -twoway- plot >to our histogram, and because those plots will be drawn after the histogram >bars, they will overlay the bars. > >Here is a simple example using the auto data set. > > . sysuse auto > . hist mpg, addplot(pci 0 20 .1 20) > >In the -addplot()- option, we specified the immediate form of the parallel >coordinates plot, -pci-. (We could have used other plottypes, but this seemed >easiest.) With the 2 supplied coordinates, we are just connecting the line >from the point (y=0,x=20) to (y=.1,x=20) -- a vertical line at x=20. I had >already peeked at the histogram and seen that the y-axis ranged from 0 to .1. > >If Eric wants more vertical lines, he can just add more sets of coordinates. >Eric may also want to add the option -legend(off)- because -histogram- assumes >that you want each of your plots identified, and I doubt that Eric does. > >Note that if we add more coordinates pairs, each line will be drawn in the >same style -- color, thickness, and pattern. All of the lines are a single >plot and thus share a style. A little-known feature of -addplot()- is that >you can add more than one plot and thus draw plots with different styles. >Just separate the plots with a -||- as you would on the -twoway- command. >Expanding on our example, > > . hist mpg, addplot(pci 0 20 .1 20 0 30 .1 30 || pci 0 25 .1 25) > >Draws vertical lines at 20 and at 30 with a common style, and another line at >25 (from the second -pci-) with a different style. We can also change the >look of any of the plots using the standard -lcolor()-, -lwidth()-, and >-lpattern()- options allowed on all -pci- plots. > >We can even add plots of a different type, say labeled marker symbols, by >adding something like -|| scatteri .05 35 "my text"- after the last -pci- >specification. > >-- Vince > vwiggins@stata.com > * * 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/

**References**:**Re: st: Additional lines on histogram***From:*vwiggins@stata.com (Vince Wiggins, StataCorp)

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