Extras.Rmd

---
title: "R Notebook"
output: html_notebook
---

### Special variable .Last.value
The special variable *.Last.value* prints the results of the last valid expression :
```{r}
a=1.2 
1/a 
```
and access the contents of *.Last.value* :
```{r}
.Last.value 
```

### Source and sink
The file *commands.R* contains some R code. This is an R script file. Let us have a look at the contents of it :
```{r}
cat(readLines("commands.R"), sep="\n") 
```

The run the R commands that are contained within a script file, use the function *source()* : 
```{r}
source("commands.R")
```

It is possible to redirect the output of running commands and functions into a text file on disk using *sink()*. The function *sink()* will divert all subsequent output from the console to an external file, ‘record.lis’. The second call will close the file.
```{r}
sink("record.lis")
i <- 1:30
outer(i, i, "*")
sink()
```

To make sure the file has been created on the filesystem : 
```{r}
list.files(".","record")
```