You are currently browsing the monthly archive for March 2015.
We’ve added a new cheatsheet to our collection. Data Visualization with ggplot2 describes how to build a plot with ggplot2 and the grammar of graphics. You will find helpful reminders of how to use:
- coordinate systems
- position adjustments
- legends, and
The cheatsheet also documents tips on zooming.
Download the cheatsheet here.
Bonus – Frans van Dunné of Innovate Online has provided Spanish translations of the Data Wrangling, R Markdown, Shiny, and Package Development cheatsheets. Download them at the bottom of the cheatsheet gallery.
We’ve added a new cheatsheet to our collection! Package Development with devtools will help you find the most useful functions for building packages in R. The cheatsheet will walk you through the steps of building a package from:
- Setting up the package structure
- Adding a DESCRIPTION file
- Writing code
- Writing tests
- Writing documentation with roxygen
- Adding data sets
- Building a NAMESPACE, and
- Including vignettes
The sheet focuses on Hadley Wickham’s devtools package, and it is a useful supplement to Hadley’s book R Packages, which you can read online at r-pkgs.had.co.nz.
Download the sheet here.
Bonus – Vivian Zhang of SupStat Analytics has kindly translated the existing Data Wrangling, R Markdown, and Shiny cheatsheets into Chinese. You can download the translations at the bottom of the cheatsheet gallery.
I’m pleased to announced that the new haven package is now available on CRAN. Haven makes it easy to read data from SAS, SPSS and Stata. Haven has the same goal as the foreign package, but it:
- Can read binary SAS7BDAT files.
- Can read Stata13 files.
- Always returns a data frame.
(Haven also has experimental support for writing SPSS and Stata data. This still has some rough edges but please try it out and report any problems that you find.)
Haven is a binding to the excellent ReadStat C library by Evan Miller. Haven wouldn’t be possible without his hard work – thanks Evan! I’d also like to thank Matt Shotwell who spend a lot of time reverse engineering the SAS binary data format, and Dennis Fisher who tested the SAS code with thousands of SAS files.
Using haven is easy:
- Install it,
- Load it,
- Then pick the appropriate read function:
These only need the name of the path. (
read_sas() optionally also takes the path to a catolog file.)
All functions return a data frame:
- The output also has class
tbl_dfwhich will improve the default print method (to only show the first ten rows and the variables that fit on one screen) if you have dplyr loaded. If you don’t use dplyr, it has no effect.
- Variable labels are attached as an attribute to each variable. These are not printed (because they tend to be long), but if you have a preview version of RStudio, you’ll see them in the revamped viewer pane.
- Missing values in numeric variables should be seemlessly converted. Missing values in character variables are converted to the empty string,
"": if you want to convert them to missing values, use
- Dates are converted in to
Dates, and datetimes to
POSIXcts. Time variables are read into a new class called
hmswhich represents an offset in seconds from midnight. It has
format()methods to nicely display times, but otherwise behaves like an integer vector.
- Variables with labelled values are turned into a new
labelledclass, as described next.
SAS, Stata and SPSS all have the notion of a “labelled” variable. These are similar to factors, but:
- Integer, numeric and character vectors can be labelled.
- Not every value must be associated with a label.
Factors, by contrast, are always integers and every integer value must be associated with a label.
Haven provides a
labelled class to model these objects. It doesn’t implement any common methods, but instead focusses of ways to turn a labelled variable into standard R variable:
as_factor(): turns labelled integers into factors. Any values that don’t have a label associated with them will become a missing value. (NB: there’s no way to make
as.factor()work with labelled variables, so you’ll need to use this new function.)
zap_labels(): turns any labelled values into missing values. This deals with the common pattern where you have a continuous variable that has missing values indiciated by sentinel values.
If you have a use case that’s not covered by these function, please let me know.