Using CUT and Quartile to generate breaks in R function

Question

Following some great advice from before, I'm now writing my 2nd R function and using a similar logic. However, I'm trying to automate a bit more and may be getting too smart for my own good.

I want to break the clients into quintiles based on the number of orders. Here's my code to do so:

# sample data clientID <- round(runif(200,min=2000, max=3000),0) orders <- round(runif(200,min=1, max=50),0)  df <- df <- data.frame(cbind(clientID,orders))  #function to break them into quintiles ApplyQuintiles <- function(x) {   cut(x, breaks=c(quantile(df$orders, probs = seq(0, 1, by = 0.20))),        labels=c("0-20","20-40","40-60","60-80","80-100")) }  #Add the quintile to the dataframe df$Quintile <- sapply(df$orders, ApplyQuintiles) 

table(df$Quintile)

0-20   20-40   40-60    60-80   80-100  40     39      44       38      36 

You'll see here that in my sample data, I created 200 observations, yet only 197 are listed via table. The 3 left off are NA

Now, there are some clientIDs that have an 'NA' for quintile. It seems if they were at the lowest break, in this case, 1, then they were not included in the cut function.

Is there a way to make cut inclusive of all observations?

Answer 1

Try the following:

set.seed(700)  clientID <- round(runif(200,min=2000, max=3000),0) orders <- round(runif(200,min=1, max=50),0)  df <- df <- data.frame(cbind(clientID,orders))  ApplyQuintiles <- function(x) {   cut(x, breaks=c(quantile(df$orders, probs = seq(0, 1, by = 0.20))),        labels=c("0-20","20-40","40-60","60-80","80-100"), include.lowest=TRUE) } df$Quintile <- sapply(df$orders, ApplyQuintiles) table(df$Quintile)  0-20  20-40  40-60  60-80 80-100    40     41     39     40     40  

I included include.lowest=TRUE in your cut function, which seems to make it work. See ?cut for more details.

Answer 2

There is also cut2 in the venerable Hmisc package. It does quantile cuts.

From the help:

Function like cut but left endpoints are inclusive and labels are of the form [lower, upper), except that last interval is [lower,upper]. If cuts are given, will by default make sure that cuts include entire range of x. Also, if cuts are not given, will cut x into quantile groups (g given) or groups with a given minimum number of observations (m). Whereas cut creates a category object, cut2 creates a factor object.