#====================
# Figure 12.1.R.
# Two linear equations plotted.
#====================
x1=(0:100)*8/100  # Range of x1 values from 0 to 8.
x2.A=2+(1/4)*x1   # x2 values for line A.
x2.B=5-(1/2)*x1   # x2 values for line B
x2=cbind(x2.A,x2.B)  # Combine both sets of x2 values
                     #  into a matrix, as columns.
matplot(x1,x2,type="l",lty=c(1,1),col=c(1,1))
                  # Plot both columns of x2 vs x1,
                  #  line type (lty) solid (1),
                  #  color (col) black (1).