Basic Plotting in "Modeling Techniques in Predictive Analytics" - r

Question

I am trying to plot the x and y pairs as demonstrated below. Can someone provide me with the basic code to plot x1, y1? I've tried a number of things to include plot(x1,y1) and its not recognizing these variables.
# The Anscsombe Quartet in R
# demonstration data from
# Anscombe, F. J. 1973, February. Graphs in statistical analysis.
# The American Statistician 27: 17â21.
# define the anscombe data frame
anscombe <- data.frame(
x1 = c(10, 8, 13, 9, 11, 14, 6, 4, 12, 7, 5),
x2 = c(10, 8, 13, 9, 11, 14, 6, 4, 12, 7, 5),
x3 = c(10, 8, 13, 9, 11, 14, 6, 4, 12, 7, 5),
x4 = c(8, 8, 8, 8, 8, 8, 8, 19, 8, 8, 8),
y1 = c(8.04, 6.95, 7.58, 8.81, 8.33, 9.96, 7.24, 4.26,10.84, 4.82, 5.68),
y2 = c(9.14, 8.14, 8.74, 8.77, 9.26, 8.1, 6.13, 3.1, 9.13, 7.26, 4.74),
y3 = c(7.46, 6.77, 12.74, 7.11, 7.81, 8.84, 6.08, 5.39, 8.15, 6.42, 5.73),
y4 = c(6.58, 5.76, 7.71, 8.84, 8.47, 7.04, 5.25, 12.5, 5.56, 7.91, 6.89))
# show results from four regression analyses
with(anscombe, print(summary(lm(y1 ~ x1))))
with(anscombe, print(summary(lm(y2 ~ x2))))
with(anscombe, print(summary(lm(y3 ~ x3))))
with(anscombe, print(summary(lm(y4 ~ x4))))
# place four plots on one page using standard R graphics
# ensuring that all have the same scales
# for horizontal and vertical axes
pdf(file = "fig_more_anscombe.pdf", width = 8.5, height = 8.5)
par(mfrow=c(2,2),mar=c(3,3,3,1))
with(anscombe, plot(x1, y1, xlim=c(2,20),ylim=c(2,14),
pch = 19, col = "darkblue", cex = 2, las = 1)
title("Set I")
with(anscombe,plot(x2, y2, xlim=c(2,20),ylim=c(2,14),
pch = 19, col = "darkblue", cex = 2, las = 1))
title("Set II")
with(anscombe,plot(x3, y3, xlim=c(2,20),ylim=c(2,14),
pch = 19, col = "darkblue", cex = 2, las = 1))
title("Set III")
with(anscombe,plot(x4, y4, xlim=c(2,20),ylim=c(2,14),
pch = 19, col = "darkblue", cex = 2, las = 1))
title("Set IV")
dev.off()
par(mfrow=c(1,1),mar=c(5.1, 4.1, 4.1, 2.1)) # return to plotting defaults
# suggestions for the student
# see if you can develop a quartet of your own
# or perhaps just a duet...
# two very different data sets with the same fitted model

Answer 1

Note that anscombe data set comes with R out of the box and does not have to be defined.
The code below sets up a 2x2 grid for plotting and then calculates the overall range for the x and separately for the y variables. Then for i = 1, 2, 3, 4 it creates the ith formula and plots it using the calculated ranges. as.roman is used to get the roman numeral portion of the title. Then we perform a linear regression. We could have just written fm <- lm(fo, anscombe) to calculate the regression but had we done that, the print(summary(fm)) output would have shown literally fo as the formula which is not very nice. Finally we plot the regression line using abline and print the summary.
Try this:
par(mfrow = c(2,2))
xrange <- range(anscombe[1:4])
yrange <- range(anscombe[5:8])
for(i in 1:4) {
fo <- as.formula( sprintf("y%d ~ x%d", i, i) )
plot(fo, anscombe, xlim = xrange, ylim = yrange, main = paste("Set", as.roman(i)))
fm <- do.call("lm", list(fo, quote(anscombe)))
abline(fm)
print( summary(fm) )
}
par(mfrow = c(1,1))
giving this plot (output from print(summary(...)) not shown):

Answer 2

If all you want to do is plot x1 and y1, try:
plot(anscombe$x1,anscombe$y1)
or (from your code):
with(anscombe, plot(x1, y1, xlim=c(2,20),ylim=c(2,14),
pch = 19, col = "darkblue", cex = 2, las = 1)
Your above code is plotting them to a pdf file, starting at the line:
pdf(file = "fig_more_anscombe.pdf", width = 8.5, height = 8.5)
and not ending until you terminate the pdf at:
dev.off()
If you don't terminate the pdf, you will never see a plot output in R. If you have run the code multiple times, make sure no pdf devices are open by running:
dev.off()
until you see:
Error in dev.off() : cannot shut down device 1 (the null device)