De tablas a gráficos, presentaciones en Stata
Stata has few facilities for presentation graphics, largely because it is
aimed at more or less advanced technical people rather than lay or business
people. However, for many purposes even very advanced users often would
benefit from having access to more tools for display, especially of raw data
or of results that come in tabular form with text labels attached.
In this talk I survey various programs, mostly written for Stata 6.0.
tabm, tabsort and tabsplit
allow the tabulation of (respectively) multiple variables with similar scales,
variables sorted by rows or columns or both, and string variables split into
parts.
hplot is a graphical workhorse that can produce a variety of
horizontally labelled plots for data, including W.S. Cleveland's dot charts
or dot plots; variations on them with continuous rather than dotted lines;
D.R. McNeil's horizontal parallel line plots; and displays for showing key
quantities with or without confidence intervals.
hbar produces a horizontal bar charts. Bars for different
variables are stacked with base at 0, depending on whether values are positive
or negative. Optionally, bars may be horizontal lines with or without vertical
line s at either or both ends.
The symbols for hplot go beyond the standard Stata set as
implemented in graph, symbol() and the
shadings for hbar include no shading and invisible bars, the
last allowing some special effects.
One of the main advantages of hplot and hbar
is that plenty of space is available for longer text labels. You are not
obliged by space or by Stata rules to use labels no more than 8 characters in
length. Equally simple but equally important is that all text is written
horizontally, thus avoiding `giraffe graphics', in which you must hold your
head at varying angles to read the text.
Given hplot and hbar it is easy to write
drivers for specialised variants. tabhplot
and tabhbar represent tables of frequencies, while
cihplot displays confidence intervals.
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