Question

Supposed I am pulling the synonyms of “help” by the function of synonyms() from wordnet and get the followings:

Str = synonyms("help")    
Str
[1] "c(\"aid\", \"assist\", \"assistance\", \"help\")"     
[2] "c(\"aid\", \"assistance\", \"help\")"                 
[3] "c(\"assistant\", \"helper\", \"help\", \"supporter\")"
[4] "c(\"avail\", \"help\", \"service\")"  

Then I can get a one character string using

unique(unlist(lapply(parse(text=Str),eval)))

at the end that looks like this:

[1] "aid"        "assist"     "assistance" "help"       "assistant"  "helper"     "supporter" 
[8] "avail"      "service"

The above process was suggested by Gabor Grothendieck. His/Her solution is good, but I still couldn’t figure out that if I change the query term into “company”, “boy”, or someone else, an error message will be responsed.

One possible reason maybe due to the “sixth” synonym of “company” (please see below) is a single term and does not follow the format of “c(\”company\”)”.

synonyms("company")

[1] "c(\"caller\", \"company\")"                                    
[2] "c(\"company\", \"companionship\", \"fellowship\", \"society\")"
[3] "c(\"company\", \"troupe\")"                                    
[4] "c(\"party\", \"company\")"                                     
[5] "c(\"ship's company\", \"company\")"                            
[6] "company"

Could someone kindly help me to solve this problem.
Many thanks.

Answer 1

You can solve this by creating a little helper function that uses R’s try mechanism to catch errors. In this case, if the eval produces an error, then return the original string, else return the result of eval:

Create a helper function:

evalOrValue <- function(expr, ...){
  z <- try(eval(expr, ...), TRUE)
  if(inherits(z, "try-error")) as.character(expr) else unlist(z)
}

unique(unlist(sapply(parse(text=Str), evalOrValue)))

Produces:

[1] "caller"         "company"        "companionship" 
[4] "fellowship"     "society"        "troupe"        
[7] "party"          "ship's company"

---

I reproduced your data and then used dput to reproduce it here:

Str <- c("c(\"caller\", \"company\")", "c(\"company\", \"companionship\", \"fellowship\", \"society\")", 
"c(\"company\", \"troupe\")", "c(\"party\", \"company\")", "c(\"ship's company\", \"company\")", 
"company")