Writing dictionary addition function in R

Question

I need to write the equivalent of the following code in R but I'm not quite sure how to go about it:

def add(args):
  result = args["a"] + args["b"]
  return result

The reason why is because for the platform I am using (Cloudera Data Science Workbench) models need a JSON input to be able to call them using an API key

So if I write a test model in R such as:

f <- function(x, y) {
    return (x + y)
}

I cannot do a call like {"x" : 2, "y" : 4} using the httr package.

So I either need to make a dictionary like call for functions in R

OR

I am simply calling JSON incorrectly in which case could someone help me format that correctly for an API call

Thanks

Do you just want to create the character string `{"x" : 2, "y" : 4}`? Do you have a named list e.g. `list(x = 2, y = 4)`? — danlooo, Oct 07 '21 at 14:09
@danlooo yes that would be ideal. It's frustrating that the API call needs to be in JSON format so every function needs to be a python dictionary type or R list type. No named list I just want to deploy a simple addition function and call it then in R using the API key using `httr::POST` — M00N KNIGHT, Oct 07 '21 at 14:15

danlooo · Answer 1 · 2021-10-07T14:44:29.747

1

JSON is the default data format for most REST APIs. We can serialize an R list to JSON using the jsonlite package. The other way of creating an R list based on a json string is also possible:

library(jsonlite)

# named lists
l <- list(x = 2, y = 4)
l
#> $x
#> [1] 2
#> 
#> $y
#> [1] 4
c <- "{\"x\":3,\"y\":5}"
c
#> [1] "{\"x\":3,\"y\":5}"

toJSON(l, auto_unbox = TRUE)
#> {"x":2,"y":4}
fromJSON(c, simplifyVector = TRUE)
#> $x
#> [1] 3
#> 
#> $y
#> [1] 5

# vector without names
toJSON(c(1,2,3), auto_unbox = TRUE)
#> [1,2,3]
fromJSON("[4,5,6]", simplifyVector = TRUE)
#> [1] 4 5 6

^{Created on 2021-10-07 by the reprex package (v2.0.1)}

edited Oct 07 '21 at 14:44

answered Oct 07 '21 at 14:28

danlooo

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The `toJSON` function is great thanks! so just in addition then (pardon the pun), how would I create the addition function in a way that I can call the arguments from the rest API as we have expressed above in JSON format? – M00N KNIGHT Oct 07 '21 at 14:33
For example if I deploy that addition model in R, writing the arguments in JSON format for the rest API doesnt make sense because they dont have names – M00N KNIGHT Oct 07 '21 at 14:35
@M00NKNIGHT I revised my answer. – danlooo Oct 07 '21 at 14:41

score 0 · Accepted Answer · answered Oct 07 '21 at 15:30

Thanks @danlooo for the help. Along with my own research I came up with an answer that satisfies my question

As the rest API needs a key-value pair format on CSDW, I can do the following taken from @danlooos answer:

f <- function(l) {
    return (l$a + l$b)
}

f(list(a = 2, b = 3) # Returns 5

This can be put into JSON format then for the API call as:

{"a" : 2, "b" : 3}

Writing dictionary addition function in R

2 Answers2