Calculations for policies without claims
NMydata <- data.frame(cbind(NClaim$claim_nb, NClaim$pol_duration,
NClaim$pol_sit_duration, NClaim$drv_age1, NClaim$drv_age2,
NClaim$vh_value, NClaim$vh_age, NClaim$vh_cyl, NClaim$vh_speed,
NClaim$vh_weight,NClaim$vh_din))
NMean <- with(NClaim, sapply(NMydata, mean, na.rm = TRUE))
NSD <- with(NClaim, sapply(NMydata, sd, na.rm = TRUE))