将定界字符串转换为数据帧中的数字矢量

Question

This is such a basic question, I'm embarrassed to ask.

Let's say I have a dataframe full of columns which contain data of the following form:

test <-"3000,9843,9291,2161,3458,2347,22925,55836,2890,2824,2848,2805,2808,2775,2760,2706,2727,2688,2727,2658,2654,2588"

I want to convert this to a numeric vector, which I have done like so:

test <- as.numeric(unlist(strsplit(test, split=",")))

I now want to convert a large dataframe containing a column full of this data into a numeric vector equivalent:

mutate(data,
  converted = as.numeric(unlist(strsplit(badColumn, split=","))),
)

This doesn't work because presumably it's converting the entire column into a numeric vector and then replacing a single row with that value:

Error in mutate_impl(.data, dots) : Column converted must be length 20 (the number of rows) or one, not 1274

How do I do this?

Answer 1

This might help:

library(purrr)

mutate(data, converted = map(badColumn, function(txt) as.numeric(unlist(strsplit(txt, split = ",")))))

What you get is a list column which contains the numeric vectors.

Answer 2

Base R

A=c(as.numeric(strsplit(test,',')[[1]]))

A
[1]  3000  9843  9291  2161  3458  2347 22925 55836  2890  2824  2848  2805  2808  2775  2760  2706  2727  2688  2727  2658  2654  2588


df$NEw2=lapply(df$NEw, function(x) c(as.numeric(strsplit(x,',')[[1]])))

df%>%mutate(NEw2=list(c(as.numeric(strsplit(NEw,',')[[1]]))))

Answer 3

Here's some sample data that reproduces your error:

data <- data.frame(a = 1:3, 
                   badColumn = c("10,20,30,40,50", "1,2,3,4,5,6", "9,8,7,6,5,4,3"), 
                   stringsAsFactors = FALSE)

Here's the error:

library(tidyverse)
mutate(data, converted = as.numeric(unlist(strsplit(badColumn, split=","))))
# Error in mutate_impl(.data, dots) : 
#   Column `converted` must be length 3 (the number of rows) or one, not 18

A straightforward way would be to just use strsplit on the entire column, and lapply ... as.numeric to convert the resulting list values from character vectors to numeric vectors.

x <- mutate(data, converted = lapply(strsplit(badColumn, ",", TRUE), as.numeric))
str(x)
# 'data.frame': 3 obs. of  3 variables:
#  $ a        : int  1 2 3
#  $ badColumn: chr  "10,20,30,40,50" "1,2,3,4,5,6" "9,8,7,6,5,4,3"
#  $ converted:List of 3
#   ..$ : num  10 20 30 40 50
#   ..$ : num  1 2 3 4 5 6
#   ..$ : num  9 8 7 6 5 4 3