## demonstration of scatterplots, loess, and the like
## ADM 10/21/2007

## look at the effects of ideology on voting in civil liberties cases
load("civlib.Rda")
print(civlib)

## crate a scatterplot
plot(civlib$ideology, civlib$civlib)

## add some labels
plot(civlib$ideology, civlib$civlib, xlab="Ideology",
   ylab="% Liberal in Civil Liberties Cases")

## add a loess (local regression) line
plot(civlib$ideology, civlib$civlib, xlab="Ideology",
   ylab="% Liberal in Civil Liberties Cases")
lines(loess.smooth(civlib$ideology, civlib$civlib))

## change the width and color of line
plot(civlib$ideology, civlib$civlib, xlab="Ideology",
   ylab="% Liberal in Civil Liberties Cases")
lines(loess.smooth(civlib$ideology, civlib$civlib), lwd=3, col="red")

## add a least squares (OLS) line
plot(civlib$ideology, civlib$civlib, xlab="Ideology",
   ylab="% Liberal in Civil Liberties Cases")
abline(lm(civlib$civlib~civlib$ideology), lwd=3, col="red")

## compute the correlation coefficient
cor(civlib$ideology, civlib$civlib)