library(openxlsx)

df<-read.xlsx("http://kanggc.iptime.org/book/data/describe-e.xlsx")
df_dat<-data.matrix(df)

cpi<-df_dat[,2]
interest<-df_dat[,3]
gdp<-df_dat[,4]
deflator<-df_dat[,5]

df_new<-cbind(cpi, interest, gdp, deflator)
df_new

(var<-var(df_new))
df_var<-data.matrix(var)
(sd<-sqrt(diag(df_var)))

corr<-cor(df_new)
corr

df_new_1<-cbind(cpi/100, interest/100, gdp/100, deflator/100)
(var_new<-var(df_new_1))
(corr<-cor(df_new_1))