Miguel123 - 2 months ago 14

R Question

I have a data frame that contains numbers and numbers separated by a "." and I want to change the entries dependent on the "." string.

If the entry does not contain a "." the prefix "-" should be added. That's kind of simple using the subsetting or grep functionality. But I also want to replace the entries which contain a "." with the counter of ".".

my example data:

`X1 X2`

1 2

3 4

6 8

5 1.2

3.4 7

1.2.5 9

11 3.4.7

and I would like to have it look like this:

`X1 X2`

-1 -2

-3 -4

-6 -8

-5 1

2 -7

3 -9

-11 4

I have no clue and tried already subsetting, extracting the "." parts to count them. But I can not insert the counter. Thanks for your help.

Answer

Here it is with data.table The idea is to create a counter in an temporary column:

```
library(data.table)
dt<-data.table(df)
dt$X1 <- as.character(dt$X1 )
dt$X2 <- as.character(dt$X2 )
dt[!grepl(".", dt$X1, fixed=TRUE),X1:=paste("-", X1, sep="") ]
dt[!grepl(".", dt$X2, fixed=TRUE),X2:=paste("-", X2, sep="") ]
dt[grepl(".", dt$X1, fixed=TRUE)|grepl(".", dt$X2, fixed=TRUE), count_point:=as.character(sequence(.N))]
dt[grepl(".", dt$X1, fixed=TRUE),X1:=count_point]
dt[grepl(".", dt$X2, fixed=TRUE),X2:=count_point]
df <- data.frame(dt[, c("X1", "X2"), with = FALSE])
```

There should be a way to do it in less line, using `.SD`