Get a list of numbers from range(s) of number

问题

I have a data frame where one column contains a range (or ranges) of numbers. I would like to turn this into a list of numbers based of the given range.

Example input:

"35-40"

"35-43, 45-47"

This should yield:

[1]  35 36 37 38 39 40

and

[1]  35 36 37 38 39 40 41 42 43 45 46 47

回答1:

We can do a split and with Map, get the numbers

do.call(Map, c(`:`, lapply(strsplit(df1$v1, '-'), as.numeric)))
#[[1]]
# [1] 35 36 37 38 39 40 41 42 43 44 45

#[[2]]
#[1] 43 44 45 46 47

If we need to find the sequence within the string

lapply(strsplit(df1$v1, "-"), function(x) Reduce(`:`, as.numeric(x)))
#[1]]
#[1] 35 36 37 38 39 40 41 42 43

#[[2]]
#[1] 45 46 47

Update

If we have multiple elements in a string

df1 <- structure(list(v1 = c("35-43", "45-47", "30-42, 25-27")), 
.Names = "v1", row.names = c(NA, 
 -3L), class = "data.frame")

lapply(strsplit(df1$v1, ", "), function(x) do.call(c, 
    lapply(strsplit(x, "-"), function(y) Reduce(`:`, as.numeric(y)))))

data

df1 <- structure(list(v1 = c("35-43", "45-47")), .Names = "v1", row.names = c(NA, 
-2L), class = "data.frame")

回答2:

You can use eval(parse(...)) as follows,

eval(parse(text = sub('-', ':', '35-40')))
#[1] 35 36 37 38 39 40

unlist(lapply(sub('-', ':', c('35-40', '45-47')), function(i) eval(parse(text = i))))
#[1] 35 36 37 38 39 40 45 46 47

EDIT

Based on your latest edit, then,

unlist(lapply(strsplit(x, ', '), function(i) {
           ind <- sub('-', ':', i); unlist(lapply(ind, function(j) eval(parse(text = j))))
  }))

 #[1] 35 36 37 38 39 40 41 42 43 45 46 47

回答3:

we use substr to extract parts of string to get beginning and end of numeric list. we use as.numeric to convert strings extracted to numbers. we use the colon to create the list of numbers . it will also work for multiple parts of list

> input
[1] "35-40"
> instart=substr(input,1,2)
> instart
[1] "35"
> inend=substr(input,4,5)
> inend
[1] "40"
> newlist=as.numeric(instart):as.numeric(inend)
> newlist
[1] 35 36 37 38 39 40

来源：https://stackoverflow.com/questions/45435153/get-a-list-of-numbers-from-ranges-of-number

标签

list

dataframe

numbers

range