grcomb -- create and combine several single graphs into one
grcomb graph command var1[*#] var2[*#] var3[*#] var4[*#] [...] [if] [ in] , varblock(#) [order(abab|aabb) name(name[, replace]) draw feedback graph options]
by is not allowed. Weights are not allowed.
grcomb allows you to generate, in a single command, several graphs of the same type and using the same options; to optionally display them; and to combine them into a single graph window. It is a wrapper for Stata's built-in graph commands, in particular the graph combine command.
grcomb options will now be further described using the following two examples. In each example, it is supposed that you want to combine three single graphs into a combined graph:
(1) scatter a1 b, jitter(8) scatter a2 b, jitter(8) scatter a3 b, jitter(8)
This is achieved by grcomb scatter a1 b a2 b a3 b, v(2) jitter(8)
(2) scatter a1 b1, jitter(8) scatter a2 b2, jitter(8) scatter a3 b3, jitter(8)
This is achieved by grcomb scatter a1 b1 a2 b2 a3 b3, v(2) jitter(8)
var*# replaces var with # copies of itself in grcomb's varlist. The purpose of this option will become clear shortly.
varblock(#) specifies the number of variables for a single graph command. In both examples (1) and (2), the single scatter commands each take two variables as arguments. Therefore, varblock is 2 in both cases. If the single graph commands were histogram, varblock would be 1, since histograms take only one variable as argument.
order(abab|aabb) specifies the order of the variables in grcomb's varlist. The default is order(abab) and is exemplified by both examples (1) and (2), where the variables for the single graph commands sequentially follow each other in grcomb's varlist (e.g. in (2), a1 is plotted against b1, a2 is plotted against b2, and a3 is plotted against b3). Specifiying order(aabb) requires the variables to be listed in the order a1 a2 a3 b1 b2 b3 (example (2)). The point of this option is to allow simplifying the varlist to a* b* (or maybe a? b?). I.e. given that a1-a3 and b1-b3 are the only variables starting with letters "a" and "b", respectively, the grcomb command in example (2) can be shortened to grcomb scatter a* b*, v(2) order(aabb) jitter(8). Example (1), in turn, could be simplified to grcomb scatter a* b*3, v(2) order(aabb) jitter(8), since, by way of cashing in option var*#, b*3 expands to b b b. (Don't confuse the wildcard asterisk ,*' with the multiply operator ,*' of option var*#.)
name(name[, replace]) lets you enter a name for the combined graph and optionally replace any previous graph of the same name. But grcomb automatically names your graphs for you, so you don't usually need this option.
draw displays the single graphs. If you omit this option, display of the single graphs (e.g. the three scatter plots in examples (1) and (2)) is suppressed.
feedback shows feedback on grcomb's progress in terms of the number of single graph commands it has processed.
graph options include all the options possible with the single graph command. In examples (1) and (2), this would be the jitter(8) option. You can specify here any number of options that are allowed with the single graph command you've chosen.
grcomb may run into trouble if you have a variable in your data set with the same name as (one of the words of) your single graph command. It will recognize this for the first word of your single graph command, but not for any potential subsequent words.
Example: If you have a variable scatter in your data set and you type grcomb scatter var1 var2 var3 var4, v(2), grcomb will catch the error and ask you to remove or rename variable scatter. However, if you type grcomb twoway scatter var1 var2 var3 var4, v(2), grcomb will crash without any helpful error message.
grcomb gives unique names to both the single and the combined graphs it produces, so that none of the graphs produced by any single or consecutive calls to grcomb will be overwritten. (If you must know, the names correspond to the number of seconds expired since midnight, prefixed with the letter "g".)
By default, grcomb uses the altshrink option of Stata's graph combine command. At present, there's nothing you can do to change this (except editing out the word "altshrink" from "grcomb.ado".)
Plotting temperature vs pressure for five timepoints
Awkward version: . grcomb scatter temperature1 pressure1 temperature2 pressure2 temperature3 pressure3 temperature4 pressure4 temperature5 pressure5, v(2)
Elegant version: . grcomb scatter temperature* pressure*, v(2) order(aabb)
Displaying single graphs, and feedback . grcomb spineplot education sex incomeclass sex, v(2) draw f
Graph commands with different numbers of arguments
Combine 3 histograms: . grcomb hist age height bmi, v(1) bins(10) percent
Combine 2 scatterplots: . grcomb scatter sales returns year nemploy nlayoff year, v(3)
Multi-word graph commands . grcomb graph twoway bar income nchildren education*2, v(2) order(aabb)
Alex Gamma, University Hospital of Psychiatry, Zurich, Switzerland. Email: firstname.lastname@example.org
Manual: [G] graph combine
Online: [G] graph_combine, spineplot (if installed)