Category: R

John Mount builds a function to improve upon the group-by to mutate model in dplyr:

The advantages of the shorthand are:

• The analyst only has to specify the grouping column once.
• The data (mtcars) enters the pipeline only once.
• The analyst doesn’t have to start thinking about joins immediately.

Frankly I’ve never liked the shorthand. I feel it is a “magic extra” that a new user would have no way of anticipating from common use of group_by() and summarize(). I very much like the idea of wrapping this important common use case into a single verb. Adjoining “windowed” or group-calculated columns is a common and important step in analysis, and well worth having its own verb.

Below is our attempt at elevating this pattern into a packaged verb.

Click through for the script.  I’d like to see something like this make its way into dplyr.

Michael Grogan has a few tips for data cleaning with R:

6. Delete observations using head and tail functions

The head and tail functions can be used if we wish to delete certain observations from a variable, e.g. Sales. The head function allows us to delete the first 30 rows, while the tail function allows us to delete the last 30 rows.

When it comes to using a variable edited in this way for calculation purposes, e.g. a regression, the as.matrix function is also used to convert the variable into matrix format:

Salesminus30days←head(Sales,-30)
X1=as.matrix(Salesminus30days)
X1

Salesplus30days<-tail(Sales,-30)
X2=as.matrix(Salesplus30days)
X2

Some of these tips are for people familiar with Excel but fairly new to R.  These also use the base library rather than the tidyverse packages (e.g., using merge instead of dplyr’s join or as.date instead of lubridate).  You may consider that a small negative, but if it is, it’s a very small one.

S. Richter-Walsh explains seven important dplyr functions with plenty of examples:

There are many useful functions contained within the dplyr package. This post does not attempt to cover them all but does look at the major functions that are commonly used in data manipulation tasks. These are:

select() 
filter()
mutate() 
group_by() 
summarise()
arrange() 
join()

The data used in this post are taken from the UCI Machine Learning Repository and contain census information from 1994 for the USA. The dataset can be used for classification of income class in a machine learning setting and can be obtained here.

That’s probably the bare minimum you should know about dplyr, but knowing just these seven can make data analysis in R much easier.

Tristan Mahr explains what tibbles and tribbles are and how they compare to built-in data frames:

The name “tribble” is short for “transposed tibble” (the transposed part referring to change from column-wise creation in tibble() to row-wise creation in tribble()).

I like to use light-weight tribbles for two particular tasks:

• Recoding: Create a tribble of, say, labels for a plot and join it onto a dataset.

• Exclusion: Identify observations to exclude, and remove them with an anti-join.

I’ve been more used to data frames than tibbles, but this post shows some interesting things you can do with tibbles a lot more easily than with data frames.  It’s enough to make me want to use tibbles more frequently.  H/T R-bloggers