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Sunday, March 11, 2012

Creating a Graph


Creating a Graph

In R, graphs are typically created interactively.
# Creating a Graph
attach(mtcars)
plot(wt, mpg)
abline(lm(mpg~wt))
title("Regression of MPG on Weight")
The plot( ) function opens a graph widow and plots weight vs. miles per gallon.
The next line of code adds a regression line to this graph. The final line adds a title.
plot example click to view

Saving Graphs

You can save the graph in a variety of formats from the menu
File -> Save As.
You can also save the graph via code using one of the following functions.

Function Output to
pdf("mygraph.pdf") pdf file
win.metafile("mygraph.wmf") windows metafile
png("mygraph.png") png file
jpeg("mygraph.jpg") jpeg file
bmp("mygraph.bmp") bmp file
postscript("mygraph.ps") postscript file
See input/output for details.

Viewing Several Graphs

Creating a new graph by issuing a high level plotting command (plot, hist, boxplot, etc.) will typically overwrite a previous graph. To avoid this, open a new graph window before creating a new graph. To open a new graph window use one of the functions below.

Function Platform
windows() Windows
X11() Unix
quartz() Mac
You can have multiple graph windows open at one time. See help(dev.cur) for more details.
Alternatively, after opening the first graph window, choose History -> Recording from the graph window menu. Then you can use Previous and Next to step through the graphs you have created.

Graphical Parameters

You can specify fonts, colors, line styles, axes, reference lines, etc. by specifying graphical parameters. This allows a wide degree of customization. Graphical parameters, are coverd in the Advanced Graphs section. The Advanced Graphs section also includes a more detailed coverage of axis and text customization.
 
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