Scatterplots in Base R

Here we introduce scatterplots in base R. The codes are simple, but you should also remember the options that make the plots more informative, like adding colors, legends, and error bars.

Continuous Data

Error Bars

Another common task is to add error bars to a set of data points. This can be accomplished using the arrows command. The arrows command takes two pairs of coordinates, two pairs of x and y values. The command then draws a line between each pair and adds an "arrow head" with a given length and angle.

> plot(x,y,xlab="Independent",ylab="Dependent",main="Random Stuff")
> xHigh <- x
> yHigh <- y + abs(rnorm(10,sd=3.5))
> xLow <- x
> yLow <- y - abs(rnorm(10,sd=3.1))
> arrows(xHigh,yHigh,xLow,yLow,col=2,angle=90,length=0.1,code=3)

Figure 2. A data set with error bars added.

Note that the option code is used to specify where the bars are drawn. Its value can be 1, 2, or 3. If code is 1 the bars are drawn at pairs given in the first argument. If code is 2 the bars are drawn at the pairs given in the second argument. If code is 3 the bars are drawn at both.