Working with Mathematica and R - Clojure Data Analysis - page 216

How it works…

To call an R function, we make a series of method calls on the RConnection object that we
created in Setting up R to talk to Clojure . The irst call, eval , takes the code to evaluate as a
string and passes it to R.

Next, we have to convert the output to a Clojure data structure. We irst call asList on the
result, which converts it to a type that implements java.lag.Iterable . This can be passed
to map , which is used to convert the list's members to doubles.

There's more…

The example in this recipe called the R function qr . This calculates the QR decomposition of
a matrix. For more information on this function, see http://www.math.montana.edu/
Rweb/Rhelp/qr.html .

Passing vectors into R

In order to do very complex or meaningful analysis, we'll need to be able to pass vector or
matrix data into R to operate on and analyze.

Let's see how to do this.

Getting ready

We must irst complete the recipe, Setting up R to talk to Clojure , and have Rserve running.
We must also have the Clojure-speciic parts of that recipe done and the connection to
Rserve made.

We'll also need access to the clojure.string namespace:

(require '[clojure.string :as str])

How to do it…

To make passing values into R easier, we'll irst deine a protocol and then we'll use it to pass
a matrix to R:

1. In order to handle the conversion of all the data types into a string that R can read,

we'll deine a protocol, ToR . Any data types that we want to marshal into R must
implement this, as follows:
(defprotocol ToR
(->r [x] "Convert an item to R."))