Unwanteed period added to "in" when making a JSON from data frame (R jsonlite)

Question

When generating a JSON object from a data frame in R, "in" is converted to "in." and I'm not sure how to solve this. Any help would be appreciated!

library(jsonlite)

query_json3 <- data.frame("eClass" = c("Fermentation","Sample", "ResultValue","Experiment"), 
                         "collection" = c("fermentations","samples", "resultValues", "experiments"))
filters1 <- data.frame("field" = "attributes.experiment", 
                      "value" = "EXP-EB-22-019")
filters2 <- data.frame("field" = "originID", 
                       "in" = "fermentations.originID")
filters3 <- data.frame("field" = "SubjectID", 
                       "in" = "samples.id")
filters4 <- data.frame("field" = "type", 
                       "value" = "Small-Scale Screening")

query_json3[1, "filters"][[1]] <- list(filters1)
query_json3[2, "filters"][[1]] <- list(filters2)
query_json3[3, "filters"][[1]] <- list(filters3)
query_json3[4, "filters"][[1]] <- list(filters4)

toJSON(query_json3)

Output:

[{"eClass":"Fermentation","collection":"fermentations","filters":[{"field":"attributes.experiment","value":"EXP-EB-22-019"}]},{"eClass":"Sample","collection":"samples","filters":[{"field":"originID","in.":"fermentations.originID"}]},{"eClass":"ResultValue","collection":"resultValues","filters":[{"field":"SubjectID","in.":"samples.id"}]},{"eClass":"Experiment","collection":"experiments","filters":[{"field":"type","value":"Small-Scale Screening"}]}] 

Desired output:

[{"eClass":"Fermentation","collection":"fermentations","filters":[{"field":"attributes.experiment","value":"EXP-EB-22-019"}]},{"eClass":"Sample","collection":"samples","filters":[{"field":"originID","in":"fermentations.originID"}]},{"eClass":"ResultValue","collection":"resultValues","filters":[{"field":"SubjectID","in":"samples.id"}]},{"eClass":"Experiment","collection":"experiments","filters":[{"field":"type","value":"Small-Scale Screening"}]}] 

Answer 1

The smoking gun is not jsonlite here. in is a reserved keyword in R, and for this reason, data.frame adds the period. You can use check.names=FALSE:

data.frame("field" = "SubjectID", 
           "in" = "samples.id")
#       field        in.
# 1 SubjectID samples.id
data.frame("field" = "SubjectID", 
           "in" = "samples.id", 
           check.names = FALSE)
#       field         in
# 1 SubjectID samples.id