从字符串中提取数字，如果它后面跟着 R 中的某些字符

Question

I have a dataframe with a variable that contains food quantities in different measurement units. The dataframe contains ~11000 observations.

Let me give you this example: "10gr peterselie, 7 Grams look, 5g kruiden en 400GRAMM bouillon, 2 tbsp olive-oil, 1oz ketchup, 20 grapes, 1 gelbe Paprika"

I found a way to extract the numbers and sum them up, using this function:

sum_numerics <- function(x) {

  # Grab all numbers that appear 
  matches <- str_match_all(x, "[0-9]+")

  # Grab the matches column in the list, transform to numeric, then sum
  sapply(matches, function(y) sum(as.numeric(y)))

}

What I'm looking for is a way to extract all food quantities that are in grams and write them into a new variable to sum them up in the next step. I spend some time looking for ways to do this and spend some time solving the problem with the regex-demo , but I can't find a working solution and I really can't figure out how to write working regex-functions. Shame on me!

User "Max Teflon" provided a possible solution that looks, after some more investigation, like this:

get_gramms <- function(x) {

# Grab all numbers that appear
str_extract_all(x, "([0-9]+\\s?([gG]|[gGrRaAmM]{5,6}|[gGrRaAmM]{2}))") %>% # any number followed by an optional space and a small/capital g%>%

unlist() %>%

str_remove_all('[[:alpha:]]') %>% # a vector is what we want

str_trim() %>% # remove all trailing whitespaces

as.numeric() # change to numbers

}

x %>%
mutate(var = map(var,~get_gramms(.))) %>%
mutate(var = map_dbl(var,~ifelse(length(.)>0,sum(.),NA)))

I think his answer is close to solving my problem, but it still returns wrong values, for example for "1 gelbe Paprika".

Looking forward to new ideas, solutions!

Answer 1

You could use a look-ahead assertion and remove the whitespaces afterwards:

library(tidyverse)
x <- "10gr peterselie, 7 Grams look, 5g kruiden en 400GRAMM bouillon, 2 tbsp olive-oil, 1oz ketchup"

sum_numerics <- function(x) {

  # Grab all numbers that appear 
  str_match_all(x, "[0-9]+\\s?(?=[gG])") %>% # any number followed by an optional space and a small/capital g
    unlist() %>% # a vector is what we want
    str_trim() %>% # remove all trailing whitespaces
    as.numeric() %>% # change to number
    sum() # sum it up

}
sum_numerics(x)
#> [1] 422

Or, if you just want to get all the numbers and use them afterwards:

library(tidyverse)
x <- "10gr peterselie, 7 Grams look, 5g kruiden en 400GRAMM bouillon, 2 tbsp olive-oil, 1oz ketchup"

get_gramms <- function(x) {

  # Grab all numbers that appear 
  str_match_all(x, "[0-9]+\\s?(?=[gG])") %>% # any number followed by an optional space and a small/capital g
    unlist() %>% # a vector is what we want
    str_trim() %>% # remove all trailing whitespaces
    as.numeric() # change to numbers
}
get_gramms(x)
#> [1]  10   7   5 400

Note that the whitespace can not be put into the assertion since it is optional and an assertion needs a fixed length.

Answer 2

Maybe you can try the code below, using gsub() + regmatches() + gregexpr() from base R

r <- sum(as.numeric(gsub("(\\d+).*",
                         "\\1",
                         unlist(regmatches(s,gregexpr("\\d+\\s?(g|gr|grams|gram)\\b",s,ignore.case = T))))))

such that

> r
[1] 422

DATA

s <- "10gr peterselie, 7 Grams look, 5g kruiden en 400GRAMM bouillon, 2 tbsp olive-oil, 1oz ketchup"

EDIT : If you want to the manipulation along a column, maybe you can do it like below

f <- Vectorize(function(s) {
  sum(as.numeric(gsub("(\\d+).*",
                      "\\1",
                      unlist(regmatches(s,gregexpr("\\d+\\s?(g|gr|grams|gram)\\b",s,ignore.case = T))))))
}
)

df <- within(df, y <- f(x))
df <- within(df, y <- ifelse(y==0,NA,1))

Answer 3

This is somewhat ugly but we can use:

sum(as.numeric(unlist(sapply(strsplit(my_string,","),
        function(x) stringr::str_extract_all(gsub("\\s","",x),
                "\\d+(?=[gG][rams]?)")))))#credit to ThomasisCoding(learnt something new)
[1] 422

Data:

my_string<-"10gr peterselie, 7 Grams look, 5g kruiden en 400GRAMM bouillon, 2 tbsp olive-oil, 1oz ketchup"

Answer 4

Using str_extract_all

library(stringr)

str_extract_all(my_string,"[0-9]+(?=[ ]{0,2}[gG])")[[1]] %>% 
  as.numeric()%>%
  sum()

[1] 422

if now you have a vector of strings:

mystrings <- c("10gr peterselie, 7 Grams look, 5g kruiden en 400GRAMM bouillon, 2 tbsp olive-oil, 1oz ketchup",
               "but also 5g of something and 10 Gr of other stuffs")

str_extract_all(mystrings,"[0-9]+(?=[ ]{0,2}[gG])") %>%
  lapply(.,function(x) as.numeric(x) %>%
           sum()
         )

[[1]]
[1] 422

[[2]]
[1] 15