There are a lot of questions and answers on the internet. This page lists resources that I have found useful, so I thought you might find them useful too.
Step one: download R to your appropriate system (Windows, Mac, and Linux).
Step two: download RStudio. RStudio has invested a lot of time and money to make using R much, much easier. It’s also free!
To learn R, you need to learn how to get unstuck with R. This teaches you a really good process to iterate through when going through the process of getting unstuck.
To learn a new function or package, Quick-R, provides nice quick description of functions and other R-related things.
For all my other problems, I usually google the error message, or try my darndest to ask an reasonable question to google that describes my current dilemna, and then look read the appropriate blog post, or StackOVerflow Answer. RSeek is also basically a google search that filters by R related content.
To stay up to date with what other people around the world are doing with R, I recommend checking up on r-bloggers every other day, and checking out the #rstats hashtag on twitter. The R and statistics community on twitter is both excellent and friendly.
Got a basic handle on R and are hankering for more? I recommend these free, online books by Hadley Wickham:
There is also a book, Ramarro, by quantide which seems similar(ish) to Hadley’s books.
S3 classes are this really awesome minimal class of functions that can be super handy in R. They are described nicely in Hadley’s book, but I have also found these to be helpful:
This blog post, which also has such a suave blog layout.
If you are going to do a plot in R, it should be in ggplot. It takes about 5 minutes to get the hang of, and once you’ve got it down you can create plots that make sense, behave how you expect, look fantastic.
ggplot ollows a logical syntax adapted from the book “The Grammar of Graphics”. It makes visualisation make sense. And there are lots of other packages that build upon it to make it more awesome, such as GGally.
So here are some ggplot resources in order of usefulness
Plotly for R, written and maintained by Carson Sievert, is a very powerful and flexible interactive plotting enging in R. It has a fully fledged API for writing interactice graphics in R, as well as a fantastic function that gives the user a lot for free:
ggplotly. You can read more about plotly for R in Carson’s free and online book.
ggvis is another great package written by Hadley Wickham, which builds upon the structure of ggplot but it allows for more interactive, reactive, plot building. Examples can be found here here, and here.
More serious development on ggvis will apparently begin in 2018, as Hadley and his team at RStudio will be spending 2017 to make the everything in the tidyverse work well together. For the moment I would recommend using plotly to do your interactive graphics.
shiny is a really awesome way to enhance your R plotting, and turn them into ‘apps’ (although whether they are actually apps is questionable, in my opinion).
Probably the coolest thing ever.
knitr is this amazing package that allows the user to combine their code and document text, making research easier to reproduce, and it does this while looking slick and classy. The idea is essentially to let the human do the writing, and the computer handle displaying the results, so that reports can be easily constructed, and most importantly, reproduced easily.
You can also augment your rmarkdown documents with templates. For example - rticles which is an r package that adds loads of rmarkdown templates. Currently, there are templates for the R Journal, the UseR Conference, Journal of Statistical Software, PLoS Computational Biology, and more!
I use decision trees a lot in R, and I even wrote a little package that helps take care of some common tasks in interrogating decision trees. Here are a list of resources that I recommend using to learn about them:
This book from James et al - chapter 8 specifically refers to decision trees. They’ve also made the book free! Also their videos on decision trees are very useful. You can find a comprehensive list of all their videos and material at this website
This book chapter from the Handbook of Statistics is broad and general.
This video on introduction to boosting trees for regression and classification by statsoft.
STATA do a great job of explaining multilevel and hierarchical models on their blog. I found these two blogs and video really helpful:
Just as it is important to have strong data visualisation skills, it is important to understand what makes a good looking document, poster, business card, and whatnot. To this end, you should read typography in ten minutes, and the summary of key rules of typography. One day I will purchase some fonts to pay him back.