Starting numbering from value in R-CodePudding

I have a very simple dataset such as:

datfra <- data.frame(ID = c(2, 3, 5, 4, 1),
                     Species = c("bluewhale", "bluewhale","bndolphin","bluewhale","whalesp"))

Looking:

> datfra
  ID   Species
1  2 bluewhale
2  3 bluewhale
3  5 bndolphin
4  4 bluewhale
5  1   whalesp

I would like to add a 3rd column, numbering the rows, but starting from a certain specific number, something like:

strartingfrom <- 15

datfra <- datfra %>% arrange(ID) %>% mutate(newID = row_number(from=strartingfrom))

Obviously the from inside row_number doesn't work. Anyone has an elegant way to number rows starting at a different number to 1?

Should look like:

  newID ID   Species
1    16  1   whalesp
2    17  2 bluewhale
3    18  3 bluewhale
4    19  4 bluewhale
5    20  5 bndolphin

[EDIT]

I got it solved just trying a simmple approach:

datfra <- datfra %>% arrange(ID) %>% mutate(newID = strartingfrom   row_number())

CodePudding user response：

You can directly try this:

datfra <- datfra %>% 
    arrange(ID) %>% 
    mutate(newID = strartingfrom:(strartingfrom   nrow(datfra) - 1))

Or make a function:

newID_row_number <- function(dt, start_from, by_id="ID") {
  dt <- dt %>% 
    arrange(!!as.name(by_id)) %>% 
    mutate(newID = start_from:(start_from nrow(dt)-1))
  return(dt)
}

strartingfrom <- 15

datfra <- newID_row_number(datfra, strartingfrom)

CodePudding user response：

May be you can use this :

start = 10
datfra$newID = seq(start, nrow(datfra) start-1)

CodePudding user response：

Use `:`() and order().

i <- 15  ## define start
transform(datfra[order(datfra$ID), ], new=15:(15   nrow(datfra) - 1))
#   ID   Species new
# 5  1   whalesp  15
# 1  2 bluewhale  16
# 2  3 bluewhale  17
# 4  4 bluewhale  18
# 3  5 bndolphin  19