121_sources.Rmd

<style>@import url(style.css);</style>
[Introduction to Data Analysis](index.html "Course index")

# Sources

Here's a selection of links cited in the course material. The list is not yet complete, so this page is not mentioned in the course listings.

```{r links, echo = FALSE, results='asis'}
##
## ida.links(): list all Markdown links in a list of pages
##
ida.links <- function(x = 0:12, detail = FALSE) {
  x = ida.files(x)
  # parse
  links <- sapply(x, FUN = function(x) {
    conn <- file(x)
    text <- readLines(conn, warn = FALSE)
    text <- text[grepl("(\\[[a-z-]+\\]): http(.*)", text)]
    close(conn)
    text
  })
  # format
  if(!detail)
    links <- unique(unlist(links))
  return(links)
}
##
## ida.sources(): return Markdown links extracted from the course pages
##
ida.sources = function(x) {
  x = lapply(x, FUN = function(x) {
  l = ida.links(x)
  # links with titles and bracket author
  l = gsub("(\\[[a-z-]+\\]): http(.*) \"(.*)\\((.*)\\)\"", "[\\3](http\\2) (\\4)", l)
  # links with titles 
  l = gsub("(\\[[a-z-]+\\]): http(.*) \"(.*)\"", "[\\3](http\\2)", l)
  # links without titles
  l = l[-which(grepl("(\\[[a-z-]+\\]): http(.*)", l))] ## "\\1(http\\2)"
  # print
  if(length(l) > 0) {
    cat("\n\n## Session ", x, "\n")
    cat(paste("*", l), sep = "\n")
    }
  })
}
##
## show all sessions
##
ida.sources(1:12)
```