The graphics capabilities in Splus are an interactive, informative,
and
flexible
way to look at data. In order to plot graphs in Splus it is necessary
to open a graphics device:You can open a graphics window with the (Splus) command:
> motif()or
> trellis.device()To exit the graphics device use:
> dev.off()Yo need to open the graphics window before asking for the graph of something. Some basic graphics commands are:
There are several options for the graphical commands:
- barplot(x)
- creates a bar graph.
- boxplot(x)
- produces side by side boxplots from a number of vectors.
- contour(x)
- make a contour plot and possibly return coordinates of contour lines.
- coplot(x)
- produces a Conditioning Plot in the current graphics device which shows how a response depends on a predictor given another predictor.
- dotchart(x)
- plots a dot chart from a vector.
- faces(x)
- represents each multivariate observation as a face.
- hist(x)
- creates a histogram.
- pairs(x)
- creates on the current graphics device a figure which contains all of the scatterplots of one variable against another.
- persp(x)
- creates a perspective plot given a matrix that represents heights on an evenly spaced grid. Axes and/or a box may be placed on the plot.
- pie(x)
- creates a pie chart from a vector of data.
- plclust(x)
- creates a plot of a clustering tree given a structure produced by hclust.
- plot(x,y) )
- creates a scatterplot.
- qqnorm(x)
- produces a graphical display to test the distribution of data.
- qqplot(x)
- produces a graphical display to test the distribution of data.
- stars(x)
- creates star plots from a matrix of multivariate data.
- stem(x)
- prints a stem-and-leaf display for the given data. The form of the display can be produced automatically, or be controlled by the user.
- usa (x)
- puts all or part of the United States on the current or a new plot, with or without state boundaries.
The function par() can be used to set graphical parameters which stay in effect throughout all plotting until they are reset in another call to par or by invoking a new graphic device.
- abline(a, b)
- draws the line y= a+ b*x.
- abline(coef)
- vector containing the intercept a and slope b of the line y= a+ b*x.
- abline(reg)
- a regression object, such as returned by lsfit. Specifically, reg$coef, if it is of length 2, will be used to define the intercept and slope of the line. If reg$coef is of length 1, it is treated as the slope of a fit through the origin. The first two elements are used if reg$coef has length greater than 2.
- abline(h=a)
- draws the line y=a.
- abline(v=a)
- draws the line x=a.
- arrows(x1,y1,x2,y2)
- adds arrows from (x1,y1) to (x2,y2)
- axes
- adds the x- and y- axes
- axis(n)
- adds an axis to a specified side, n-1 is the x-axis, n=2 is the y-axis.
- axis(n,at=x,labels=s,pos=y,las=m)
- adds an axis to side n and puts the labels s at the positions x. x and s are vectors of the same lenght. pos shifts the axis to go through the coordinate x. las=0 adds the labels parallel to the axis, las=1 always adds horizontal labels, and las=2 rotates all labels by 45 degrees.
- box()
- adds the aouter box.
- lines(x,y)
- adds lines to an existing figure
- points(x,y)
- adds points to an existing figure
- segments(x1,y1,x2,y2)
- adds segments from (x1,y1) to (x2,y2)
- text(xpos,ypos,text)
- adds text at the specified locations
- mtext("string",side= )
- adds text in the margins of the current plot
- side specifies the side on which the text is to be placed
- bottom
- left (default)
- top
- right
- title("title",subtitle")
- adss a title and/or subtitle
- title(main= , sub= , xlab= , ylab= )
- adds titles and/or axis labels to the current plot
- will overwrite any existing titles and/or axis labels
- legend(x,y,legend= )
- puts a box at the specified x,y coordinates with examples (if possible) of the lines/points/shading used in the graph identified by user-defined text
- identify(x,y,labels= )
- similar to legend(), identify() prints text (labels) at the specified points
- locator(n= ,type= )
- returns the coordinates specified interactively on a plot
- default is n=500, type="n"
- by changing type, points and/or lines may be added to the plot
- the locator() function can be used within the function legend() or identify() instead of specifying the x and y coordinates: legend(locator(1),legend)
- the point is identified by placing the cursor over the point and pressing the left mouse button
- to exit locator without identifying all "n" points, press the middle mouse button
> par(mfrow=c(2,3))
* it is possible to specify the number and
arrangement of graphs on a page using the
mfrow= option
* mfrow=c(2,3) allows 6 plots to appear on
a page (2 rows of 6 plots each)
* because the mfrow argument was used within
the par function, the set up will stay in effect
for all subsequent graphs
> par(mfrow=c(1,1))
* restores the normal one-graph-per-page form
* this could also be done by invoking a new
graphic device
> X11()
> par(mfcol=c(3,2))
* the page is set up as above except that the
graphs are printed columnwise, mfrow prints
graphs row by row
The following arguments can be specified either by the par() function or within
a graphics function (for temporary parameter settings which stay in effect only for
the call to the function and are then reset to their previous values).
Basic symbols Superimposed symbols Filled in symbols
0 square 7 0 and 4 15 square
1 octagon 8 3 and 4 16 octagon
2 triangle 9 3 and 5 17 triangle
3 cross 10 1 and 3 18 diamond
4 X 11 2 and 6
5 diamond 12 0 and 3
6 inverted triangle 13 1 and 4
14 0 and 2