# Simple linear regression example in R:  Cross-national fertility
# Chris Adolph

# Load data
data <- read.csv("robeymore.csv",header=TRUE,na.strings="")
completedata <- na.omit(data)
attach(completedata)

# Transform variables
contraceptors <- contraceptors/100

# Run linear regression
res.lm <- lm(tfr~contraceptors)
print(summary(res.lm))

# Get predicted values
pred.lm <- predict(res.lm)

# Make a plot of the data
plot(x=contraceptors,
     y=tfr,
     ylab="Fertility Rate",
     xlab="% of women using contraception",
     main="Average fertility rates & contraception; \n
           50 developing countries",
     xaxp=c(0,1,5)
     )

# Add predicted values to the plot
points(x=contraceptors,y=pred.lm,pch=16,col="red")