labcurve {Hmisc}  R Documentation 
Label Curves, Make Keys, and Interactively Draw Points and Curves
Description
labcurve
optionally draws a set of curves then labels the curves.
A variety of methods for drawing labels are implemented, ranging from
positioning using the mouse to automatic labeling to automatic placement
of key symbols with manual placement of key legends to automatic
placement of legends. For automatic positioning of labels or keys, a
curve is labeled at a point that is maximally separated from all of the
other curves. Gaps occurring when curves do not start or end at the
same xcoordinates are given preference for positioning labels. If
labels are offset from the curves (the default behaviour), if the
closest curve to curve i is above curve i, curve i is labeled below its
line. If the closest curve is below curve i, curve i is labeled above
its line. These directions are reversed if the resulting labels would
appear outside the plot region.
Both ordinary lines and step functions are handled, and there is an option to draw the labels at the same angle as the curve within a local window.
Unless the mouse is used to position labels or plotting symbols are
placed along the curves to distinguish them, curves are examined at 100
(by default) equally spaced points over the range of xcoordinates in
the current plot area. Linear interpolation is used to get
ycoordinates to line up (step function or constant interpolation is
used for step functions). There is an option to instead examine all
curves at the set of unique xcoordinates found by unioning the
xcoordinates of all the curves. This option is especially useful when
plotting step functions. By setting adj="auto"
you can have
labcurve
try to optimally left or rightjustify labels depending
on the slope of the curves at the points at which labels would be
centered (plus a vertical offset). This is especially useful when
labels must be placed on steep curve sections.
You can use the on top
method to write (short) curve names
directly on the curves (centered on the ycoordinate). This is
especially useful when there are many curves whose full labels would run
into each other. You can plot letters or numbers on the curves, for
example (using the keys
option), and have labcurve
use the
key
function to provide long labels for these short ones (see the
end of the example). There is another option for connecting labels to
curves using arrows. When keys
is a vector of integers, it is
taken to represent plotting symbols (pch
s), and these symbols are
plotted at equallyspaced xcoordinates on each curve (by default, using
5 points per curve). The points are offset in the xdirection between
curves so as to minimize the chance of collisions.
To add a legend defining line types, colors, or line widths with no
symbols, specify keys="lines"
, e.g., labcurve(curves,
keys="lines", lty=1:2)
.
putKey
provides a different way to use key()
by allowing
the user to specify vectors for labels, line types, plotting characters,
etc. Elements that do not apply (e.g., pch
for lines
(type="l"
)) may be NA
. When a series of points is
represented by both a symbol and a line, the corresponding elements of
both pch
and lty
, col.
, or lwd
will be
nonmissing.
putKeyEmpty
, given vectors of all the xy coordinates that have been
plotted, uses largest.empty
to find the largest empty rectangle large
enough to hold the key, and draws the key using putKey
.
drawPlot
is a simple mousedriven function for drawing series of
lines, step functions, polynomials, Bezier curves, and points, and
automatically labeling the point groups using labcurve
or
putKeyEmpty
. When drawPlot
is invoked it creates
temporary functions Points
, Curve
, and Abline
.
The user calls these functions inside
the call to drawPlot
to define groups of points in the order they
are defined with the mouse. Abline
is used to call abline
and not actually great a group of points. For some curve types, the
curve generated to represent the corresponding series of points is drawn
after all points are entered for that series, and this curve may be
different than the simple curve obtained by connecting points at the
mouse clicks. For example, to draw a general smooth Bezier curve the
user need only click on a few points, and she must overshoot the final
curve coordinates to define the curve. The originally entered points
are not erased once the curve is drawn. The same goes for step
functions and polynomials. If you plot()
the object returned by
drawPlot
, however, only final curves will be shown. The last
examples show how to use drawPlot
.
The largest.empty
function finds the largest rectangle that is large
enough to hold a rectangle of a given height and width, such that the
rectangle does not contain any of a given set of points. This is
used by labcurve
and putKeyEmpty
to position keys at the most
empty part of an existing plot. The default method was created by Hans
Borchers.
Usage
labcurve(curves, labels=names(curves),
method=NULL, keys=NULL, keyloc=c("auto","none"),
type="l", step.type=c("left", "right"),
xmethod=if(any(type=="s")) "unique" else "grid",
offset=NULL, xlim=NULL,
tilt=FALSE, window=NULL, npts=100, cex=NULL,
adj="auto", angle.adj.auto=30,
lty=pr$lty, lwd=pr$lwd, col.=pr$col, transparent=TRUE,
arrow.factor=1, point.inc=NULL, opts=NULL, key.opts=NULL,
empty.method=c('area','maxdim'), numbins=25,
pl=!missing(add), add=FALSE,
ylim=NULL, xlab="", ylab="",
whichLabel=1:length(curves),
grid=FALSE, xrestrict=NULL, ...)
putKey(z, labels, type, pch, lty, lwd,
cex=par('cex'), col=rep(par('col'),nc),
transparent=TRUE, plot=TRUE, key.opts=NULL, grid=FALSE)
putKeyEmpty(x, y, labels, type=NULL,
pch=NULL, lty=NULL, lwd=NULL,
cex=par('cex'), col=rep(par('col'),nc),
transparent=TRUE, plot=TRUE, key.opts=NULL,
empty.method=c('area','maxdim'),
numbins=25,
xlim=pr$usr[1:2], ylim=pr$usr[3:4], grid=FALSE)
drawPlot(..., xlim=c(0,1), ylim=c(0,1), xlab='', ylab='',
ticks=c('none','x','y','xy'),
key=FALSE, opts=NULL)
# Points(label=' ', type=c('p','r'),
# n, pch=pch.to.use[1], cex=par('cex'), col=par('col'),
# rug = c('none','x','y','xy'), ymean)
# Curve(label=' ',
# type=c('bezier','polygon','linear','pol','loess','step','gauss'),
# n=NULL, lty=1, lwd=par('lwd'), col=par('col'), degree=2,
# evaluation=100, ask=FALSE)
# Abline(\dots)
## S3 method for class 'drawPlot'
plot(x, xlab, ylab, ticks,
key=x$key, keyloc=x$keyloc, ...)
largest.empty(x, y, width=0, height=0,
numbins=25, method=c('exhaustive','rexhaustive','area','maxdim'),
xlim=pr$usr[1:2], ylim=pr$usr[3:4],
pl=FALSE, grid=FALSE)
Arguments
curves 
a list of lists, each of which have at least two components: a vector of

z 
a twoelement list specifying the coordinate of the center of the key,
e.g. 
labels 
For 
x 
see below 
y 
for 
... 
For 
width 
see below 
height 
for 
method 
For 
keys 
This causes keys (symbols or short text) to be drawn on or beside
curves, and if 
keyloc 
When 
type 
for 
step.type 
type of step functions used (default is 
xmethod 
method for generating the unique set of xcoordinates to examine (see above). Default is 
offset 
distance in yunits between the center of the label and the line being
labeled. Default is 0.75 times the height of an "m" that would be
drawn in a label. For R grid/lattice you must specify offset using
the 
xlim 
limits for searching for label positions, and is also used to set up
plots when 
tilt 
set to 
window 
width of a window, in xunits, to use in determining the local slope for tilting labels. Default is 0.5 times number of characters in the label times the xwidth of an "m" in the current character size and font. 
npts 
number of points to use if 
cex 
character size to pass to 
adj 
Default is 
angle.adj.auto 
see 
lty 
vector of line types which were used to draw the curves. This is only used when keys are drawn. If all of the line types, line widths, and line colors are the same, lines are not drawn in the key. 
lwd 
vector of line widths which were used to draw the curves.
This is only used when keys are drawn. See 
col. 
vector of integer color numbers 
col 
vector of integer color numbers for use in curve labels, symbols,
lines, and legends. Default is 
transparent 
Default is 
arrow.factor 
factor by which to multiply default arrow lengths 
point.inc 
When 
opts 
an optional list which can be used to specify any of the options
to 
key.opts 
a list of extra arguments you wish to pass to 
empty.method 
see below 
numbins 
These two arguments are passed to the 
pl 
set to 
add 
By default, when curves are actually drawn by 
ylim 
When a plot has already been started, 
xlab 
see below 
ylab 
xaxis and yaxis labels when 
whichLabel 
integer vector corresponding to 
grid 
set to 
xrestrict 
When having 
pch 
vector of plotting characters for 
plot 
set to 
ticks 
tells 
key 
for 
Details
The internal functions Points
, Curve
, Abline
have
unique arguments as follows.
label
:for
Points
andCurve
is a single character string to label that group of pointsn
:number of points to accept from the mouse. Default is to input points until a right mouse click.
rug
:for
Points
. Default is"none"
to not show the marginal x or y distributions as rug plots, for the points entered. Other possibilities are used to executescat1d
to show the marginal distribution of x, y, or both as rug plots.ymean
:for
Points
, subtracts a constant from each ycoordinate entered to make the overall meanymean
degree
:degree of polynomial to fit to points by
Curve
evaluation
:number of points at which to evaluate Bezier curves, polynomials, and other functions in
Curve
ask
:set
ask=TRUE
to give the user the opportunity to try again at specifying points for Bezier curves, step functions, and polynomials
The labcurve
function used some code from the function plot.multicurve
written
by Rod Tjoelker of The Boeing Company (tjoelker@espresso.rt.cs.boeing.com).
If there is only one curve, a label is placed at the middle xvalue,
and no fancy features such as angle
or positive/negative offsets are
used.
key
is called once (with the argument plot=FALSE
) to find the key
dimensions. Then an empty rectangle with at least these dimensions is
searched for using largest.empty
. Then key
is called again to draw
the key there, using the argument corner=c(.5,.5)
so that the center
of the rectangle can be specified to key
.
If you want to plot the data, an easier way to use labcurve
is
through xYplot
as shown in some of its examples.
Value
labcurve
returns an invisible list with components x, y, offset, adj, cex, col
, and if tilt=TRUE
,
angle
. offset
is the amount to add to y
to draw a label.
offset
is negative if the label is drawn below the line.
adj
is a vector containing the values 0, .5, 1.
largest.empty
returns a list with elements x
and y
specifying the coordinates of the center of the rectangle which was
found, and element rect
containing the 4 x
and y
coordinates of the corners of the found empty rectangle. The
area
of the rectangle is also returned.
Author(s)
Frank Harrell
Department of Biostatistics
Vanderbilt University
fh@fharrell.com
See Also
approx
, text
, legend
,
scat1d
, xYplot
, abline
Examples
n < 2:8
m < length(n)
type < c('l','l','l','l','s','l','l')
# s=step function l=ordinary line (polygon)
curves < vector('list', m)
plot(0,1,xlim=c(0,1),ylim=c(2.5,4),type='n')
set.seed(39)
for(i in 1:m) {
x < sort(runif(n[i]))
y < rnorm(n[i])
lines(x, y, lty=i, type=type[i], col=i)
curves[[i]] < list(x=x,y=y)
}
labels < paste('Label for',letters[1:m])
labcurve(curves, labels, tilt=TRUE, type=type, col=1:m)
# Put only single letters on curves at points of
# maximum space, and use key() to define the letters,
# with automatic positioning of the key in the most empty
# part of the plot
# Have labcurve do the plotting, leaving extra space for key
names(curves) < labels
labcurve(curves, keys=letters[1:m], type=type, col=1:m,
pl=TRUE, ylim=c(2.5,4))
# Put plotting symbols at equallyspaced points,
# with a key for the symbols, ignoring line types
labcurve(curves, keys=1:m, lty=1, type=type, col=1:m,
pl=TRUE, ylim=c(2.5,4))
# Plot and label two curves, with line parameters specified with data
set.seed(191)
ages.f < sort(rnorm(50,20,7))
ages.m < sort(rnorm(40,19,7))
height.f < pmin(ages.f,21)*.2+60
height.m < pmin(ages.m,21)*.16+63
labcurve(list(Female=list(ages.f,height.f,col=2),
Male =list(ages.m,height.m,col=3,lty='dashed')),
xlab='Age', ylab='Height', pl=TRUE)
# add ,keys=c('f','m') to label curves with single letters
# For SPlus use lty=2
# Plot power for testing two proportions vs. n for various odds ratios,
# using 0.1 as the probability of the event in the control group.
# A separate curve is plotted for each odds ratio, and the curves are
# labeled at points of maximum separation
n < seq(10, 1000, by=10)
OR < seq(.2,.9,by=.1)
pow < lapply(OR, function(or,n)list(x=n,y=bpower(p1=.1,odds.ratio=or,n=n)),
n=n)
names(pow) < format(OR)
labcurve(pow, pl=TRUE, xlab='n', ylab='Power')
# Plot some random data and find the largest empty rectangle
# that is at least .1 wide and .1 tall
x < runif(50)
y < runif(50)
plot(x, y)
z < largest.empty(x, y, .1, .1)
z
points(z,pch=3) # mark center of rectangle, or
polygon(z$rect, col='blue') # to draw the rectangle, or
#key(z$x, z$y, \dots stuff for legend)
# Use the mouse to draw a series of points using one symbol, and
# two smooth curves or straight lines (if two points are clicked),
# none of these being labeled
# d < drawPlot(Points(), Curve(), Curve())
# plot(d)
## Not run:
# Use the mouse to draw a Gaussian density, two series of points
# using 2 symbols, one Bezier curve, a step function, and raw data
# along the xaxis as a 1d scatter plot (rug plot). Draw a key.
# The density function is fit to 3 mouse clicks
# Abline draws a dotted horizontal reference line
d < drawPlot(Curve('Normal',type='gauss'),
Points('female'), Points('male'),
Curve('smooth',ask=TRUE,lty=2), Curve('step',type='s',lty=3),
Points(type='r'), Abline(h=.5, lty=2),
xlab='X', ylab='y', xlim=c(0,100), key=TRUE)
plot(d, ylab='Y')
plot(d, key=FALSE) # label groups using labcurve
## End(Not run)