用字符串中的单位提取数字

Question

I have a series of strings as below:

x <- " 20 to 80% of the sward should be between 3 and 10cm tall, 
with 20 to 80% of the sward between 10 and 30cm tall"

I want to extract the numeric values and keep the units, I have tried the following:

x <- lapply(x, function(x){gsub("[^\\d |cm\\b |mm\\b |% ]", "", x, perl = T)})

Which gives:

" 20  80%       3  10cm   20  80%     10  30cm "

What I need is:

"20 80%" "3 10cm" "20 80%" "10 30cm" 

Thanks for reading

Answer 1

We could use str_extract_all from library(stringr) to extract the elements that matches the pattern (modified based on comments from @PierreLafortune)

library(stringr)
lst <-  str_extract_all(x, '\\d+\\S*')

If the length of the list elements are the same, we can rbind them to create a matrix .

m1 <- do.call(rbind, lst)

paste the alternating columns together

v1 <- paste(m1[,c(TRUE, FALSE)], m1[,c(FALSE, TRUE)])

and convert it back to matrix .

dim(v1) <- c(nrow(m1), ncol(m1)/2)
v1
#     [,1]     [,2]     [,3]     [,4]     
#[1,] "20 80%" "3 10cm" "20 80%" "10 30cm"

Answer 2

Not particularly elegant but...

library(magrittr)
library(stringr)
library(dplyr)
library(plyr)
" 20  80%       3  10cm   20  80%     10  30cm " %>%
str_split(" ") %>%
unlist %>% 
as.data.frame %>% 
    plyr::rename(replace = c("." = "string")) %$%
    gsub(string, replacement = "", pattern = " ") %>%
    as.data.frame %>% 
    plyr::rename(replace = c("." = "string")) %>%
    filter(string != "") -> etc_etc