[R] plotting survival curves (multiple curves on single graph)

[Trey Batey]

Hello.

This is a follow-up to a question I posted last week.  With some
previous suggestions from the R-help community, I have been able to
plot survival (, hazard, and density) curves using published data for
Siler hazard parameters from a number of ethnographic populations.
Can the function below be modified, perhaps with a "for" statement, so
that multiple curves (different line types---one for each population)
are plotted on a single graph for comparison?  Thanks so much.

--Trey

The function and calls below use the data in this Excel file (feel
free to access):
https://docs.google.com/leaf?id=0B5zZGW2utJN0ZDk1NjA0ZjUtMWU0ZS00ZGQ3LWIxZTUtOWE0NGVmYWMxODJl&hl=en_US

## - plot Siler survival curve
##############################
silsurv<-function(a1,b1,a2,a3,b3)
  {
    sil=function(t)
      {
        h.t<-a1*exp(-b1*t)+a2+a3*exp(b3*t)
        S.t<-exp(-a1/b1*(1-exp(-b1*t))-a2*t+a3/b3*(1-exp(b3*t)))
        d.t<-S.t*h.t

        #return(d.t)
        return(S.t)
        #return(h.t)
      }
    t<-seq(0,90,1)
plot(t,sil(t),ylim=c(0,1),type='l',cex.lab=0.8,cex.axis=0.75,ylab='S(t)',xlab='Age
(years)')
  }

with(hazanth[1,3:7],silsurv(a1=a1,b1=b1,a2=a2,a3=a3,b3=b3));title(main=hazanth[1,1],cex.main=0.9)
 # plot for Hadza
with(hazanth[2,3:7],silsurv(a1=a1,b1=b1,a2=a2,a3=a3,b3=b3));title(main=hazanth[2,1],cex.main=0.9)
 # plot for Ache
with(hazanth[3,3:7],silsurv(a1=a1,b1=b1,a2=a2,a3=a3,b3=b3));title(main=hazanth[3,1],cex.main=0.9)
 # plot for Hiwi
with(hazanth[4,3:7],silsurv(a1=a1,b1=b1,a2=a2,a3=a3,b3=b3));title(main=hazanth[4,1],cex.main=0.9)
 # plot for !Kung
with(hazanth[5,3:7],silsurv(a1=a1,b1=b1,a2=a2,a3=a3,b3=b3));title(main=hazanth[5,1],cex.main=0.9)
 # plot for Yanomamo
with(hazanth[6,3:7],silsurv(a1=a1,b1=b1,a2=a2,a3=a3,b3=b3));title(main=hazanth[6,1],cex.main=0.9)
 # plot for Tsimane

###############################