#Load data.table for fast reads and aggreagtions
library(data.table)

# Input data files are available in the "../input/" directory.
# Read in only required columns and force to numeric to ensure that subsequent 
# aggregation when calculating medians works
train <- fread('../input/train.csv', 
               select = c('Cliente_ID', 'Producto_ID', 'Demanda_uni_equil'),
               colClasses=c(Cliente_ID="numeric",Producto_ID="numeric",Demanda_uni_equil="numeric"))

#Print first 6 rows and show that conversion from integer has been successful
head(train)
sapply(train, class)