我将PostgreSQL查询的结果作为data.frame存储在R中。其中一个“列”是integer[]数组类型。在R中，这是由RPostgreSQL包作为字符串导入的。
如何在data.frame中将字符串类型转换为数字列表类型的列（或单独的数字列）？

连接并获取数据

require(RPostgreSQL)
drv = dbDriver("PostgreSQL")
con = dbConnect(drv, host = ..., post =..., dbname =..., user=..., password=...)
df = dbGetQuery(con, query_string)
dbDisconnect(con)

最小工作示例

library(dplyr)
# randomized arrays of 10 numbers
set.seed(10)
df = data.frame(id = c(1:10)) %>%
  mutate(arrcol = lapply(id, function(X) sample(1:99, 10, replace=T)),
         arrcol = gsub("c(","{{",arrcol,fixed=T),
         arrcol = gsub(")","}}",arrcol,fixed=T))

移除支架

df$arrcol = gsub(fixed=T, "{", "", df$arrcol)
df$arrcol = gsub(fixed=T, "}", "", df$arrcol)

转换为数字列表

# Attempt 1: 
df$arrcol = as.numeric(df$arrcol)
# Error: (list) object cannot be coerced to type 'double'

# Attempt 2:
df$arrcol = lapply(df$arrcol, 
                   function(x) strsplit(x, ",", fixed=T))
# no error, but now the data appears to be stored as a list of character lists: 
# arrcol[1]: list(c("1", "2", "3", "4", "5",...

# Attempt 3:
df$arrcol = lapply(df$arrcol, 
                   function(x) as.numeric(
                     unlist(
                       strsplit(x, ",", fixed=T))
                   )
)
# this one seems to work