CRIM：per capita crime rate by town
ZN：proportion of residential land zoned for lots over 25,000 sq.ft.
INDUS：proportion of non-retail business acres per town
CHAS：Charles River dummy variable (= 1 if tract bounds river; 0 otherwise)
NOX：nitric oxides concentration (parts per 10 million)
RM：average number of rooms per dwelling
AGE：proportion of owner-occupied units built prior to 1940
DIS：weighted distances to five Boston employment centres
RAD：index of accessibility to radial highways
TAX：full-value property-tax rate per $10,000
PTRATIO：pupil-teacher ratio by town
B：1000(Bk - 0.63)^2 where Bk is the proportion of blacks by town
LSTAT：% lower status of the population
MEDV：Median value of owner-occupied homes in $1000's