#  Chapter 5: Making Controlled Comparisons
library(poliscidata)  # Loads R companion package in session

# MULTIPLE LINE CHARTS

# First we need to tranform DV and update the gssD
# Retrieve level names of variable to graph.
levels(gss$grass) 
# Create the indicator in the non-design dataset, multiplied times 100.                         
gss$grass.legal=as.numeric(gss$grass=="LEGAL") 
gss$grass.legal=100*gss$grass.legal
# Run svydesign, updating gssD to include the new indicator.
gssD = svydesign(id=~1, data=gss, weights=~wtss)

# Multiple line chart, controlled comparison
iplotC(~grass.legal,~attend3+kids,gssD,grass.legal~kids+attend3,
       xlab="Relgious attendance",
       ylab="Percent favoring legalization",
       main=list("Percentage Favoring Marijuana Legalization\n by Religious 
                 Attendance and Kids",cex=1))

# the code below layers on top of line chart created above
legend("topright",   #Locates the legend in the plotting area
       legend=c("No","Yes"), #Labels the categories
       lty=c(1,2),           #Make sure the lin types match the legend labels
       lwd=2, 		         #Specifies the same line weight shown in the graph
       title="Does R have kids?",
       inset=0.1, 	         #Specifies distance from the plot borders
       bty="n")              #Suppresses the box around the legend