RcppOctave engine examples

112-engine-RcppOctave.Rmd

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+---
+title: "Call RcppOctave from knitr"
+output:
+  html_document:
+    highlight: pygments
+---
+
+## Example
+
+Defining a matrix in `octave`/`MATLAB` is really easy
+
+```{r, engine='RcppOctave'}
+A = [ 4 5 6; 7 8 9]
+B = [ 0 1 2 ; 3 4 5 ; 6 7 8]
+E = [ A; 10 11 12]
+E(:,:, 2) = B
+```
+
+You can later get the values of the variables in `R` using RcppOctave
+
+```{r}
+library(RcppOctave)
+# List of user-defined variables and functions
+o_ls()
+# Two ways to access the variables
+o_get("A", "B", "E")
+.O$A
+.O$B
+.O$E
+```
+
+# Declaring R variables within octave
+
+You can also retrieve the variables directly to your `R` environment, using the chunk option `engine.opts=list(retrieve.vars=TRUE)`
+
+```{r, engine='RcppOctave', engine.opts=list(retrieve.vars=TRUE)}
+A = [ 2 6; 3 9]
+A *= 2
+B = [ 1 2 3; 4 5 6]
+```
+
+```{r}
+A
+B
+t(B)
+```
+
+Use this with caution, however, as you may overwrite or even delete R variables.
+
+```{r}
+C <- "This content will be overwritten"
+E <- "This variable will no longer exist"
+```
+
+```{r, engine='RcppOctave', engine.opts=list(retrieve.vars=T)}
+C = 'This is the new content for C'
+clear E
+```
+
+```{r}
+C
+E
+```
+
+# octave functions
+
+You can also define functions in octave that you can use within R
+
+```{r, engine='RcppOctave', engine.opts=list(retrieve.vars=TRUE)}
+function f = ffact(n)
+  f = prod(1:n)
+```
+
+```{r}
+ffact(10)
+```
+
+Notice however, that overwritten standard octave functions will not be accessible from R
+
+```{r, engine='RcppOctave', engine.opts=list(retrieve.vars=TRUE)}
+function f = fact(n)
+  f = prod(1:n)
+```
+
+```{r}
+fact(10)
+```
+
+`fact` is a standard function in octave. In this case you need to call the function using `.O`
+
+```{r}
+.O$fact(10)
+```

112-engine-RcppOctave.md

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+---
+title: "Call RcppOctave from knitr"
+output:
+  html_document:
+    highlight: pygments
+---
+
+## Example
+
+Defining a matrix in `octave`/`MATLAB` is really easy
+
+
+```octave
+A = [ 4 5 6; 7 8 9]
+B = [ 0 1 2 ; 3 4 5 ; 6 7 8]
+E = [ A; 10 11 12]
+E(:,:, 2) = B
+```
+
+You can later get the values of the variables in `R` using RcppOctave
+
+
+```r
+library(RcppOctave)
+# List of user-defined variables and functions
+o_ls()
+```
+
+```
+## [1] "A"     "B"     "C"     "E"     "ffact"
+```
+
+```r
+# Two ways to access the variables
+o_get("A", "B", "E")
+```
+
+```
+## $A
+##      [,1] [,2] [,3]
+## [1,]    4    5    6
+## [2,]    7    8    9
+## 
+## $B
+##      [,1] [,2] [,3]
+## [1,]    0    1    2
+## [2,]    3    4    5
+## [3,]    6    7    8
+## 
+## $E
+## , , 1
+## 
+##      [,1] [,2] [,3]
+## [1,]    4    5    6
+## [2,]    7    8    9
+## [3,]   10   11   12
+## 
+## , , 2
+## 
+##      [,1] [,2] [,3]
+## [1,]    0    1    2
+## [2,]    3    4    5
+## [3,]    6    7    8
+```
+
+```r
+.O$A
+```
+
+```
+##      [,1] [,2] [,3]
+## [1,]    4    5    6
+## [2,]    7    8    9
+```
+
+```r
+.O$B
+```
+
+```
+##      [,1] [,2] [,3]
+## [1,]    0    1    2
+## [2,]    3    4    5
+## [3,]    6    7    8
+```
+
+```r
+.O$E
+```
+
+```
+## , , 1
+## 
+##      [,1] [,2] [,3]
+## [1,]    4    5    6
+## [2,]    7    8    9
+## [3,]   10   11   12
+## 
+## , , 2
+## 
+##      [,1] [,2] [,3]
+## [1,]    0    1    2
+## [2,]    3    4    5
+## [3,]    6    7    8
+```
+
+# Declaring R variables within octave
+
+You can also retrieve the variables directly to your `R` environment, using the chunk option `engine.opts=list(retrieve.vars=TRUE)`
+
+
+```octave
+A = [ 2 6; 3 9]
+A *= 2
+B = [ 1 2 3; 4 5 6]
+```
+
+
+```r
+A
+```
+
+```
+##      [,1] [,2]
+## [1,]    4   12
+## [2,]    6   18
+```
+
+```r
+B
+```
+
+```
+##      [,1] [,2] [,3]
+## [1,]    1    2    3
+## [2,]    4    5    6
+```
+
+```r
+t(B)
+```
+
+```
+##      [,1] [,2]
+## [1,]    1    4
+## [2,]    2    5
+## [3,]    3    6
+```
+
+Use this with caution, however, as you may overwrite or even delete R variables.
+
+
+```r
+C <- "This content will be overwritten"
+E <- "This variable will no longer exist"
+```
+
+
+```octave
+C = 'This is the new content for C'
+clear E
+```
+
+
+```r
+C
+```
+
+```
+## [1] "This is the new content for C"
+```
+
+```r
+E
+```
+
+```
+## Error in eval(expr, envir, enclos): object 'E' not found
+```
+
+# octave functions
+
+You can also define functions in octave that you can use within R
+
+
+```octave
+function f = ffact(n)
+  f = prod(1:n)
+```
+
+
+```r
+ffact(10)
+```
+
+```
+## [1] 3628800
+```
+
+Notice however, that overwritten standard octave functions will not be accessible from R
+
+
+```octave
+function f = fact(n)
+  f = prod(1:n)
+```
+
+
+```r
+fact(10)
+```
+
+```
+## Error in eval(expr, envir, enclos): could not find function "fact"
+```
+
+`fact` is a standard function in octave. In this case you need to call the function using `.O`
+
+
+```r
+.O$fact(10)
+```
+
+```
+## [1] 3628800
+```