Introduction to Statistics (MAT/SST 115.03 2008S)

R notes for Activity 6-1


6-1.a

6-1.a asks you to compute some proportions. You can certainly ask R to do those computations.

EnvSpend = c(398/646, 198/646, 50/646)

6-1.b

6-1.b asks you to construct a bar graph. Here's a straightforward approach.

barplot(c(398,198,50),
  main="Opinions About Federal Envt Spending",
  names.arg = c("Too Little", "Just Right", "Too Much")
)

If we care abaout proportions, rather than absolute numbers, we can use the vector we just created.

barplot(EnvSpend,
  main="Opinions About Federal Envt Spending",
  names.arg = c("Too Little", "Just Right", "Too Much")
)

6-1.i

This exercise asks you to make a stacked bar graph. You should read notes on stacked bar graphs to see how to make one in R.

If you're impatient, here are some basic instructions.

EnvironmentSpending = data.frame(
  Liberal = c(.819, .174, .007),
  Moderate = c(.619, .314, .067),
  Conservative = c(.479, .385, .136)
)
rownames(EnvironmentSpending) = c("Too Little", "About Right", "Too Much")
barplot(as.matrix(EnvironmentSpending),
  main="Political Perspectives on Environment Spending",
  col=c("green", "grey", "red")
)

To add the legend (which R likes to put in a stupid place), replace the last command with

barplot(as.matrix(EnvironmentSpending),
  main="Political Perspectives on Environment Spending",
  legend=rownames(EnvironmentSpending),
  col=c("green", "grey", "red")
)

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Samuel A. Rebelsky, rebelsky@grinnell.edu

Copyright (c) 2007-8 Samuel A. Rebelsky.

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