# ---------------------------------------------------------------------
# Program: Bivariate1.S  
#  Author: Steven M. Boker
#    Date: Thu Oct 7 12:46:36 EST 2004
#
#  Bivariate data
#
# ---------------------------------------------------------------------

# ---------------------------------------------------------------------
#  Scatterplots


graphsheet(height=6.4,width=6.4)
plot(edaStudent$ztest, edaStudent$hscgpa, 
     xlab="Entrance Exam (Z-Score)",
     ylab="High School Core GPA",
     type='p',
     pch=2)

graphsheet(height=6.4,width=6.4)
xyplot(hscgpa ~ ztest,
     data = edaStudent,
     aspect=1,
     xlab="Entrance Exam (Z-Score)",
     ylab="High School Core GPA")

graphsheet(height=6.4,width=6.4)
xyplot(ztest ~ jitter(as.numeric(sex),5),
     data = edaStudent,
     aspect=1,
     xlab="Sex",
     ylab="Entrance Exam (Z-Score)")


# ---------------------------------------------------------------------
#  Scatterplots conditioned on a factor


graphsheet(height=6.4,width=7.5)
xyplot(hscgpa ~ ztest | sex,
     data = edaStudent,
     aspect=1,
     xlab="Entrance Exam (Z-Score)",
     ylab="High School Core GPA")


# ---------------------------------------------------------------------
#  Scatterplots conditioned on a continuous variable

graphsheet(height=6.4,width=7.5)
xyplot(hscgpa ~ ztest | cut(pposths,6),
     data = edaStudent,
     aspect=1,
     main="HSCGPA vs. ZTEST \n Cut by Probability of Post HS in Neighborhood",
     xlab="Entrance Exam (Z-Score)",
     ylab="High School Core GPA")

# ---------------------------------------------------------------------
#  Estimating a linear model

tLM <- lm(hscgpa ~ ztest, data=edaStudent)
summary(tLM)

# ---------------------------------------------------------------------
#  Plotting a regression line

graphsheet(height=6.4,width=6.4)
xyplot(hscgpa ~ ztest, 
   data = edaStudent,
   panel = function(x, y) {
      panel.xyplot(x, y)
      panel.abline(lm(hscgpa ~ ztest, data = edaStudent))
   },
   aspect=1,
   xlab="Entrance Exam (Z-Score)",
   ylab="High School Core GPA")