set.seed(95014123)
mydata <- data.frame(matrix(round(runif(100)*1000,0),nrow=50))
names(mydata) <- c("credit card usage","value")
head(mydata)
head(mydata[order(mydata[["credit card usage"]]),])

> set.seed(95014123)
> mydata <- data.frame(matrix(round(runif(100)*1000,0),nrow=50))
> names(mydata) <- c("credit card usage","value")
> head(mydata)
  credit card usage value
1               795   217
2               816   613
3               342   323
4               126   751
5               618   780
6               625   529
> head(mydata[order(mydata[["credit card usage"]]),])
   credit card usage value
47                25   109
44                81   534
18                91   985
31                99   931
19               109   190
4                126   751
>

# replace spaces with underscores
names(mydata) <- gsub(" ","_",names(mydata))
head(mydata[order(mydata$credit_card_usage),])

> # replace spaces with underscores
> names(mydata) <- gsub(" ","_",names(mydata))
> head(mydata[order(mydata$credit_card_usage),])
   credit_card_usage value
47                25   109
44                81   534
18                91   985
31                99   931
19               109   190
4                126   751
>