XX<-read.table('children.dat')
nn<-nrow(XX)



#--------------------------------
# use your student number here as a seed !!!!
#--------------------------------

set.seed(1234)


#---------------------------------
# take a sample of size n=500
#--------------------------------

n<-500
I<-sample((1:nn),n)
X<-XX[I,]
#   write.table(X,file='ownsample.dat',col.names=FALSE)



#---------------------------------------
# consider and name some columns of data matrix
#--------------------------------------------------------

m_age<-X[,2]
m_height<-X[,3]
m_weight<-X[,4]
m_smoking<-X[,5]
marital_status<-X[,6]
social_class<-X[,7]
g_age<-X[,10]
twins<-X[,12]
parity<-X[,14]
sex<-X[,15]
birth_weight<-X[,16]
dead<-X[,17]

#---------------------------------------------
# make new variables (column vectors)
#-------------------------------------------

parity.gt.0<-(parity>0)*1
parity.gt.2<-(parity>2)*1
age.gt.35<-(m_age>35)*1
boy<-(sex==1)*1
smoking<-(m_smoking>0)*1
PT<-(g_age<37)*1
LBW<-(birth_weight<250)*1