How to add a numeric value in a specific location for the whole column?-CodePudding

I have a numeric column and I would like to add the digit 0 before the last 4 digits. The columns contain numeric values, but the values have different number of digits, some have 6 digits and some have 7. So counting the numbers from the beggining will be wrong, it has to be prior to the last for digits. So, for example:

Suppose I have a column, some numbers are:

123456
1234567

I would like the result to look like this, so 0 is always the number before the last 4 digits:

1203456
12304567

I don't know if it makes sense, let me know if you need more clarification.

CodePudding user response：

We may use capture () the last four digits (\\d{4}) by adding the $ to specify the end of the string and replace with the 0 followed by the backreference (\\1) of the captured group

df1$col1 <- as.numeric(sub('(\\d{4})$', '0\\1', df1$col1))

-output

df1$col1
[1]  1203456 12304567

data

df1 <- structure(list(col1 = c(123456, 1234567)),
 class = "data.frame", row.names = c(NA, 
-2L))