wolfram alpha from R

README.md

Wolfram Alpha API from R

The attached code file provides an easy basic interface to the Wolfram Alpha API. Inspired by the wolframalpha module available for Python.

source("wa_lib.R")

Initialize client

This requires an app ID. Sign into your wolfram account to generate one.

app_id <- "" 
wa <- WolframClient(app_id)

Ask a simple question

result <- wa$query("pi")

## Querying wolfram alpha...

library(knitr)
kable(result$get_plaintext(), format = "html")

pod	id	plaintext
Input	Input	pi
Decimal approximation	DecimalApproximation	3.1415926535897932384626433832795028841971693993751058...
Property	Property	pi is a transcendental number
Number line	NumberLine
Continued fraction	ContinuedFraction	[3; 7, 15, 1, 292, 1, 1, 1, 2, 1, 3, 1, 14, 2, 1, 1, 2, 2, 2, 2, 1, 84, 2, 1, 1, 15, ...]
Alternative representations	AlternativeRepresentations:MathematicalFunctionIdentityData	pi = 180 °
Alternative representations	AlternativeRepresentations:MathematicalFunctionIdentityData	pi = -i log(-1)
Alternative representations	AlternativeRepresentations:MathematicalFunctionIdentityData	pi = cos^(-1)(-1)
Series representations	SeriesRepresentations:MathematicalFunctionIdentityData	pi = 4 sum_(k=0)^infinity (-1)^k/(2 k+1)
Series representations	SeriesRepresentations:MathematicalFunctionIdentityData	pi = -2+2 sum_(k=1)^infinity 2^k/(binomial(2 k, k))
Series representations	SeriesRepresentations:MathematicalFunctionIdentityData	pi = sum_(k=0)^infinity (50 k-6)/(2^k binomial(3 k, k))
Integral representations	IntegralRepresentations:MathematicalFunctionIdentityData	pi = 2 integral_0^infinity 1/(t^2+1) dt
Integral representations	IntegralRepresentations:MathematicalFunctionIdentityData	pi = 4 integral_0^1 sqrt(1-t^2) dt
Integral representations	IntegralRepresentations:MathematicalFunctionIdentityData	pi = 2 integral_0^infinity (sin(t))/t dt

Ask a more specific question

result <- wa$query("ion equivalents of zinc chloride")

## Querying wolfram alpha...

kable(result$get_plaintext(), format = "html")

pod	id	plaintext
Input interpretation	Input	zinc chloride | ion equivalents
Result	IonProperties:ChemicalData	Zn^(2+) (zinc) | 1 Cl^(-) (chloride) | 2

wa_lib.R

#' Basic Wolfram Alpha client and result objects
library(XML)
library(plyr)

WolframClient <- setRefClass(
  "WolframClient",
  fields = list(
    app_id = "character"
  ),
  
  methods = list(
    
    initialize = function(app_id) {
      "initialize Wolfram Alpha Client"
      
      app_id <<- app_id
    },
    
    query = function(query, quiet = TRUE) {
      "run a query against the wolfram alpha database"
      
      message("Querying wolfram alpha...")
      wa_url <- paste0("http://api.wolframalpha.com/v2/query?input=", 
                       URLencode(query), "&appid=", app_id)
      
      destfile <- tempfile()
      download.file(wa_url, destfile, method = "wget", quiet = quiet)
      result <- WolframResult(xmlInternalTreeParse(destfile))
      info <- result$get_info()
      
      if (info$success != "true" || info$error != "false")
        stop("There was a problem with this query. Please check the query infos:\n",
             paste(paste(names(info), info, sep = " = "), collapse = "\n"))
      
      return(result)
    }  
  )
)

WolframResult <- setRefClass(
  "WolframResult",
  fields = list(
    doc = "XMLInternalDocument"
  ),
  
  methods = list(
    initialize = function(doc) {
      doc <<- doc
    },
    
    xml = function() doc,
    
    get_info = function() {
      as.list(xpathApply(doc, "//queryresult", xmlAttrs)[[1]])
    },
    
    get_pods = function() {
      xpathApply(doc, "//pod")
    },
    
    get_plaintext = function() {
      ldply(get_pods(), function(pod) {
        data.frame(
          pod = xmlGetAttr(pod, "title"),
          id = xmlGetAttr(pod, "id"),
          plaintext = unlist(xpathApply(pod, "subpod/plaintext", xmlValue))
        )
      })
    }
  )
)

Hey, that's a super useful bridge between WA and R. I thought this would be great to package up and upload on CRAN for convenience. Here, I changed it slightly and pushed a packaged version of this script on Git.

It would be great if you could upload this either to CRAN or your Git, so that people can just install_github() or install() ! Here: https://github.com/ArtificialBreeze/wolfRamalpha (tested, works as is)

Has this been wrapped up into a package? If not, I'd be happy to help get it there as I think it's very useful

please feel free to wrap it into a small package for CRAN submission, that'd be fantastic. there might be some overlap with the https://cran.r-project.org/web/packages/websearchr/index.html package but see for yourself and decide whether this would be non-redundant functionality

This is very useful, much appreciated

Did this get added to CRAN? Happy to help out if needed as using this a bit at the mo. :)

I had trouble with download.file on Windows:

Error during wrapup: 'wget' call had nonzero exit status
Error: no more error handlers available (recursive errors?); invoking 'abort' restart

However, using httr works instead works fine.