How to add a new column with values based on numeric value condition in R?

I have a data frame with a colmn called concentration with numeric values.

Concentration
700657  
850789  
900123  
1011234  
750001

I want to add a new column CDrange that has values 700k+,800k+,900k+,1000k+. The values in the new column will be assigned based on the value of concentration, e.g. if value is 700657, the calculated value should be 700k+, if value is 850789 then value as 800k+ and so on. How do I write a function without using if else loops. The new column should look like

Concentration       CDrange          
700657              700k+ 
850789              800k+ 
900123              900k+ 
1011234             1000k+ 
750001              700k+

Please provide on some suggestions on how to proceed. I have tried using subset function but I am unable to keep the dataframe together.

Solution

See ?cut and ?findInterval.

df$CDrange <- cut(df$Concentration, c(700000, 800000, 900000, 1000000, Inf),
                  labels=c("700k+","800k+","900k+","1000k+") right=FALSE)