R Passing a variable into an enclosed string

Question

This may seem like a simple problem to solve, but it's beyond me. I have the following enclosed string

'{"foo":"bar","x":"<SOME VAR>"}'

I want to pass a variable into the place of <SOME VAR>. What would be the best way to achieve this? Any help is greatly appreciated.

can't you use gsub? string_name <- gsub(pattern = "<SOME VAR>", replacement = variable, x = string_name) where string_name is the name of your example string — sweetmusicality
– sweetmusicality, Commented Jun 22, 2017 at 18:51
Have you tried something like this? y <- 25; paste0('{"foo":"bar","x":"', y, '"}'). — RobertMyles
– RobertMyles, Commented Jun 22, 2017 at 19:05
@sweetmusicality That worked perfectly. Can you post that as an answer please? — Jonathan Rauscher
– Jonathan Rauscher, Commented Jun 22, 2017 at 21:21

sweetmusicality · Accepted Answer · 2017-06-22 21:29:53Z

2

(re-posting this as an answer as requested - glad to know it worked!)

can't you use gsub?

string_name <- gsub(pattern = "<SOME VAR>", replacement = variable, x = string_name)

where string_name is the name of your example string

answered Jun 22, 2017 at 21:29

sweetmusicality

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Niko · Accepted Answer · 2017-06-22 19:48:24Z

1

Can you store it as a list like:

a <- list("foo" = "bar", "x" = "<SOME VAR>")

If yes you could just fill it using the $operator:

a$x <- 3

answered Jun 22, 2017 at 19:48

Niko

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Enrique Pérez Herrero · Accepted Answer · 2017-06-22 20:19:55Z

1

Your string is, in fact, a JSON object and thus you can use any JSON parser in R to convert your data to a data.frame, easy to manipulate.

library(jsonlite)

x <- '{"foo":"bar","x":"<SOME VAR>"}'
df <- fromJSON(x)
my_value <- "This is the value I want"
df$x <- my_value
df

#$foo
#[1] "bar"
#
#$x
#[1] "This is the value I want"

You can convert the data.frame again to JSON with:

toJSON(df, auto_unbox = TRUE)

edited Jun 22, 2017 at 20:19

answered Jun 22, 2017 at 20:14

Enrique Pérez Herrero

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