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

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

Subject |
st: RE: RE: Histogram, by(var, total) |

Date |
Mon, 8 Jun 2009 10:29:05 +0100 |

I should point out that treatment of missing values should get some consideration. The code below includes observations with missing values on the -by()- variable in the total category, but excludes them from the categories shown separately. If you wanted to exclude observations with missing values from the total, you could specify expand 2 if !missing(foreign) Nick n.j.cox@durham.ac.uk -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox Sent: 07 June 2009 18:15 To: statalist@hsphsun2.harvard.edu Subject: st: RE: Histogram, by(var, total) I don't know a direct way to do this, but some trickery produces the same result. It is best explained by example. sysuse auto, clear preserve local which = _N + 1 expand 2 replace foreign = -1 in `which'/L label def origin -1 "Total", add histogram mpg, by(foreign) restore Key points: 1. -expand 2- doubles the dataset. The second half that is a copy of the first half is to be used to work out the "Total" category. 2. If the -by()- variable is integer with value labels, the extra observations should be assigned an integer value for the -by()- that is _lower_ than any other observed. You then need to define an appropriate value label. (In this case, I know that the other values are 0 and 1.) 3. You do _not_ then specify the -total- suboption, as you are using your own subterfuge to replicate it. 4. -preserve- and -restore- are optional, but note otherwise that this is a major change to the dataset. Note that Stata in no sense "knows" that the extra category is a total category, but that shouldn't matter. Now what would be done if the -by()- variable were string? At first sight, we have a problem here because "Total" would not necessarily sort first in a set of alphanumeric categories. We could use some label like "All observations" but what then if we have "Aardvarks" as a category? Here is a better trick (not to rule out the possibility of an even better trick): sysuse auto, clear preserve decode foreign, gen(Foreign) local which = _N + 1 expand 2 replace Foreign = " Total " in `which'/L histogram mpg, by(Foreign) restore The -decode- is just to produce an example with an appropriate string variable. In practice it will exist already. Notice the two small parts to the trick: (a) Putting a space before the "Total" makes it more likely to sort to the beginning of any set of categories. The space " " is a character too. (b) Putting a space afterwards ensures that the "Total" is still centred on the graph (if you care about that). But we need not worry too much about the string case. If you can't get the order you want, map the strings to integers with value labels. Naturally, nothing here is distinctive to histograms. Nick n.j.cox@durham.ac.uk *From:* Thoma, Marie E. I would like to use the "histogram yvar, by(xvar, total)" command to produce a histogram of the total and stratified variable. However, in Stata, it places the "total" graph as the last graph and I would like to have it as the first graph (before the stratified graphs). Does anyone know how to change this either using this command or another way to accomplish this same layout? * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Histogram, by(var, total)***From:*Marcello Pagano <pagano@hsph.harvard.edu>

**st: RE: Histogram, by(var, total)***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

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