Spine Plots and Spinograms
Description
Spine plots are a special cases of mosaic plots, and can be seen as a generalization of stacked (or highlighted) bar plots. Analogously, spinograms are an extension of histograms.
Usage
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18  spineplot(x, ...)
## Default S3 method:
spineplot(x, y = NULL,
breaks = NULL, tol.ylab = 0.05, off = NULL,
ylevels = NULL, col = NULL,
main = "", xlab = NULL, ylab = NULL,
xaxlabels = NULL, yaxlabels = NULL,
xlim = NULL, ylim = c(0, 1), axes = TRUE, ...)
## S3 method for class 'formula'
spineplot(formula, data = NULL,
breaks = NULL, tol.ylab = 0.05, off = NULL,
ylevels = NULL, col = NULL,
main = "", xlab = NULL, ylab = NULL,
xaxlabels = NULL, yaxlabels = NULL,
xlim = NULL, ylim = c(0, 1), axes = TRUE, ...,
subset = NULL)

Arguments
x 
an object, the default method expects either a single variable (interpreted to be the explanatory variable) or a 2way table. See details. 
y 
a 
formula 
a 
data 
an optional data frame. 
breaks 
if the explanatory variable is numeric, this controls how
it is discretized. 
tol.ylab 
convenience tolerance parameter for yaxis annotation. If the distance between two labels drops under this threshold, they are plotted equidistantly. 
off 
vertical offset between the bars (in per cent). It is fixed to

ylevels 
a character or numeric vector specifying in which order the levels of the dependent variable should be plotted. 
col 
a vector of fill colors of the same length as 
main, xlab, ylab 
character strings for annotation 
xaxlabels, yaxlabels 
character vectors for annotation of x and y axis.
Default to 
xlim, ylim 
the range of x and y values with sensible defaults. 
axes 
logical. If 
... 
additional arguments passed to 
subset 
an optional vector specifying a subset of observations to be used for plotting. 
Details
spineplot
creates either a spinogram or a spine plot. It can
be called via spineplot(x, y)
or spineplot(y ~ x)
where
y
is interpreted to be the dependent variable (and has to be
categorical) and x
the explanatory variable. x
can be
either categorical (then a spine plot is created) or numerical (then a
spinogram is plotted). Additionally, spineplot
can also be
called with only a single argument which then has to be a 2way table,
interpreted to correspond to table(x, y)
.
Both, spine plots and spinograms, are essentially mosaic plots with
special formatting of spacing and shading. Conceptually, they plot
P(y  x) against P(x). For the spine plot (where both
x and y are categorical), both quantities are approximated
by the corresponding empirical relative frequencies. For the
spinogram (where x is numerical), x is first discretized
(by calling hist
with breaks
argument) and then
empirical relative frequencies are taken.
Thus, spine plots can also be seen as a generalization of stacked bar
plots where not the heights but the widths of the bars corresponds to
the relative frequencies of x
. The heights of the bars then
correspond to the conditional relative frequencies of y
in
every x
group. Analogously, spinograms extend stacked
histograms.
Value
The table visualized is returned invisibly.
Author(s)
Achim Zeileis Achim.Zeileis@Rproject.org
References
Friendly, M. (1994), Mosaic displays for multiway contingency tables. Journal of the American Statistical Association, 89, 190–200.
Hartigan, J.A., and Kleiner, B. (1984), A mosaic of television ratings. The American Statistician, 38, 32–35.
Hofmann, H., Theus, M. (2005), Interactive graphics for visualizing conditional distributions, Unpublished Manuscript.
Hummel, J. (1996), Linked bar charts: Analysing categorical data graphically. Computational Statistics, 11, 23–33.
See Also
mosaicplot
, hist
, cdplot
Examples
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31  ## treatment and improvement of patients with rheumatoid arthritis
treatment < factor(rep(c(1, 2), c(43, 41)), levels = c(1, 2),
labels = c("placebo", "treated"))
improved < factor(rep(c(1, 2, 3, 1, 2, 3), c(29, 7, 7, 13, 7, 21)),
levels = c(1, 2, 3),
labels = c("none", "some", "marked"))
## (dependence on a categorical variable)
(spineplot(improved ~ treatment))
## applications and admissions by department at UC Berkeley
## (twoway tables)
(spineplot(margin.table(UCBAdmissions, c(3, 2)),
main = "Applications at UCB"))
(spineplot(margin.table(UCBAdmissions, c(3, 1)),
main = "Admissions at UCB"))
## NASA space shuttle oring failures
fail < factor(c(2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1,
1, 1, 1, 2, 1, 1, 1, 1, 1),
levels = c(1, 2), labels = c("no", "yes"))
temperature < c(53, 57, 58, 63, 66, 67, 67, 67, 68, 69, 70, 70,
70, 70, 72, 73, 75, 75, 76, 76, 78, 79, 81)
## (dependence on a numerical variable)
(spineplot(fail ~ temperature))
(spineplot(fail ~ temperature, breaks = 3))
(spineplot(fail ~ temperature, breaks = quantile(temperature)))
## highlighting for failures
spineplot(fail ~ temperature, ylevels = 2:1)

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