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## R

R interface for Chicken Scheme

### Overview

`R` provides a simple way to call R-functions, consisting of the following two forms: `R` and `R*`. `R` evaluates an R-expression, returning an opaque R-pointer that can be passed to other R-functions. Use this, for instance, when you don't need to modify the object in Scheme.

`R*`, on the other hand, evaluates the expression and tries to translate it into Scheme; it understands `NULL`, lists, strings, reals, bools, complex numbers and symbols. Everything else is opaque.

### Documentation

`NA`

*[constant]*

`NA → (make-NA)`

NA corresponds to R's NA.

(defineNA (make-NA))

##### Examples

Don't forget to quasiquote:

(R* (is.na (paste (c 1 ,NA)))) => #(#f => #f)

`R-missing`

*[constant]*

`R-missing → (foreign-value R_MissingArg SEXP)`

R-constant for missing arguments

(defineR-missing (foreign-value "R_MissingArg" SEXP))

##### Examples

Selecting columns of matrices; corresponds to `sum(complete.cases(airquality[, -1]))`:

(R* (sum (complete.cases (,(string->symbol "[") airquality ,R-missing 1)))) => 116

`R-null`

*[constant]*

`R-null → (foreign-value R_NilValue SEXP)`

NULL

(defineR-null (foreign-value "R_NilValue" SEXP))

##### Examples

Empty list is not null:

(R* (is.null (list))) => #f

`NULL`, on the other hand:

(R* (is.null ,R-null)) => #t

`R`

*[syntax]*

`(R expression) → R-object`

Evaluate an R-expression, but do not try to translate the result into a native Scheme object; this is useful when you don't need to manipulate the object directly in Scheme.

- expression
- The expression to evaluate

(define-syntaxR (lambda(expression rename compare) (list 'apply 'R-eval (list 'quasiquote (cdr expression)))))

##### Examples

An example from `ggplot2`:

(R (library "ggplot2")) => #<tagged pointer sexp 1bb79d8> (R (plot (qplot (factor ($ mtcars cyl)) ($ mtcars wt) data: mtcars geom: (c "boxplot" "jitter")))) => #<tagged pointer sexp 1c099f0>

Another plotting example:

(let ((x (R (sort (rnorm 47))))) (R (plot ,x xlab: "x" type: "s" main: "plot(x, type = \"s\")")) (R (points ,x cex: 0.5 col: "dark red"))) => #<tagged pointer sexp 17b90a8>

`R*`

*[syntax]*

`(R* expression) → Scheme-object`

Evaluate an R-expression and translate it into a Scheme object, where possible; use this (as opposed to `R`) when you need to manipulate the value in Scheme.

- expression
- The expression to evaluate

(define-syntaxR* (lambda(expression rename compare) `(R->scheme (R ,@(cdr expression)))))

##### Examples

An example using classical statistics:

(let* ((x (R (runif 100 0 10))) (y (R (+ 2 (+ (* 3 ,x) (rnorm 100))))) (df (R (data.frame x: ,x y: ,y))) (d (R (lm (as.formula "y ~ x") data: ,df)))) (R* ($ (summary ,d) "cov.unscaled"))) => #(0.0463194896194369 -0.0073337478838232 -0.0073337478838232 => 0.00148085390480537)

### About this egg

#### Author

#### Colophon

Documented by cock.