Using R and RStudio for Data Management, Statistical Analysis, and Graphics, 2nd Edition

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“K23166” — 2015/1/28 — 9:35 — page 133 — #159

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8.5. SPECIAL-PURPOSE PLOTS 133

plot(x1, y, pch=" ") # create an empty plot of the correct size

abline(lm(y ~ x1, subset=x2==0), lty=1, lwd=2)

abline(lm(y ~ x1, subset=x2==1), lty=2, lwd=2)

...

abline(lm(y ~ x1, subset=x2==k), lty=k+1, lwd=2)

Note: The abline() function is used to generate lines for each of the subsets, with a solid

line (lty=1) for the first group and a dashed line (lty=2) for the second (this assumes

that X

2

takes on values 0–k, see 11.1.2). The plotFun() function in the mosaic package

provides another way of adding lines or arbitrary curves to a plot.

8.5.11 Kaplan–Meier plot

Example: ...