Assign random values to column according to another column's values in R

Question

I have a dataset that has Stock Codes with the range from 2-90214 (which has around 3000 unique values). Obviously, some values between 2 and 90214 are getting skipped. I want to convert these stock codes so that they range from 1-3000 and in such a way that if the previous stock code was 1234, then everytime this number occurs, the new stock code (say 100) will be assigned.

In short, I want to convert :

Stock_Code
 1234
 5678
 4321
 1234
 5678

into :

Stock_Code
 100
 101
 102
 100
 101

How do I do this in R ?

Answer 1

We can convert the numbers into factor and then transform it into numeric

as.numeric(factor(df$StockCode))

#[1] 1 3 2 1 3

If we need it starting from 100 we can add 99 in it

as.numeric(factor(df$StockCode)) + 99

Same numbers would get same factor level which upon converting into numeric would give same numeric value

Answer 2

We can use match to get the index of the unique values, and then add 99

df1$Stock_Code <- match(df1$Stock_Code, unique(df1$Stock_Code)) + 99
df1$Stock_Code
[1] 100 101 102 100 101

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Or another option is to convert to factor and coerce to integer

with(df1, as.integer(factor(Stock_Code, levels = unique(Stock_Code)))+ 99)
#[1] 100 101 102 100 101

Answer 3

Using dplyr

library(dplyr)
dense_rank(df$Stock_Code) + 99