require(UsingR) #opens the functions and data of 
                #the package UsingR
data(kid.weights)
X=kid.weights;str(X)
pairs(X[ ,1:3] , col=X[ ,4], pch=20)

## BMI : body mass index
attach(kid.weights) #allows to write height 
            #instead of kid.weights$height...
ht_in_m = height*2.54/100        # 2.54 cm per inch
weight_in_kg = weight / 2.2046        # 2.2046 lbs. per kg
bmi = weight_in_kg/ht_in_m^2
histogram(bmi)
histogram(~bmi|gender)

library(car)
states=as.data.frame(state.x77[,c("Murder", "Population",
                        "Illiteracy", "Income", "Frost")])
scatterplotMatrix(states,spread=T,pch=20,lty.smooth=2)