One R Function A Day.

As a R user with 5 years experience, I still have some basic functions that never used or never thought they could exist. Many times I was suprised with some elegant R functions, such like strwidth, parent.frame, etc. No one can know all R functions (and it’s unnecessary), but it’s very convenient to know some basic functions, especially those in the basic packages: base, utils, stats, etc.

I used to have a learning plan: learn one R function a day. But it was terminated because I always fail to remember it. Today, once again I found a useful function of the basic package base, which impelled me to keep learning R as a daily work. How could one guy who said he has 5 years experience but still doesn’t know some basic functions?!

My plan is simple: everyday I log on my computer, one of the first tasks is reading one topic-help document. To avoid forgetting to do this, I need the help page appears automatically.

So, I need to build a topic list first, and I want to start with the base package. The following is my code:

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URL <- “http://stat.ethz.ch/R-manual/R-devel/library/base/html/”
xml<em>1 &lt;- readLines(URL)
ptn &lt;- ‘&lt;a href=\”.*?.html\”&gt;(.*?.html)&lt;/a&gt;’
xml</em>2 &lt;- regmatches(xml<em>1, regexec(ptn, xml</em>1))</p>

<p>html.list &lt;- NULL
for (i in 1:length(xml<em>2)) {
  if (length(xml</em>2[[i]]) == 2) {
    html.list &lt;- rbind(html.list, xml_2[[i]][2])
  }
}
html.list &lt;- sort(unique(html.list[-which(html.list == “00Index.html”)]))

Then I need to choose an order to load the topic one by one. The function parent.frame(2)$ofile is used to get current script’s absolute path.

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i = 0
browseURL(paste(URL, html.list[i + 1], sep = “”))
x <- paste(“i”, i+1, sep = “ <- “)
cur_code <- readLines(parent.frame(2)$ofile)
cur_code[grep(“^i “, cur_code)] <- x
writeLines(cur_code, parent.frame(2)$ofile)

The last step is creating a .bat file to run the R code in a batch mode, and add that file to your Task Scheduler and set the trigger as “at log on”. The content of the .bat file looks like this:

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 R CMD BATCH C:\Packages\base_help.R

Any kind of criticism or commet are welcome!