Is there a R function that allows you to insert a variable inside a command?-CodePudding

For example: Imagine I have an object named "cors" which contains a string only ("Spain" for example). I would like then for "cors" to be replaced in the expression (1) below by "Spain", resulting in the expression (2):

#(1)
DF <- DF %>% filter(str_detect(Country, "Germany|cors", negate = TRUE))

#(2)
DF <- DF %>% filter(str_detect(Country, "Germany|Spain", negate = TRUE))

P.S: I know that in MATLAB this could be handled with the "eval()" command, though in R it apparently has a completely different applicability.

CodePudding user response：

If we have an object, then place it outside the quotes and use paste/str_c to create the string

library(dplyr)
library(stringr)
cors <- "Spain"
pat <- str_c(c("Germany", cors),  collapse = "|")
DF %>%
    filter(str_detect(Country, pat, negate = TRUE))

Or another option is to string interpolate with glue (assuming cors object have only a single string element)

DF %>%
    filter(str_detect(Country, glue::glue("Germany|{cors}"), negate = TRUE))

Or this can be done in base R with grepl

pat <- paste(c("Germany", cors), collapse = "|")
subset(DF, !grepl(pat, Country))

CodePudding user response：

If you really want eval, you could do:

cors <- 'Spain'

DF <- DF %>% filter(
  eval(
    parse(text=paste0('str_detect(Country, "Germany|', cors, '", negate=TRUE)'))
  ))