Category: R

Steph Locke shows how to use .Rprofile to make your life easier:

First of all, you need a file called .Rprofile that’s stored in your working directory. Some useful resources about .Rprofiles can be found on .Rprofile CRAN docs and an .Rprofile intro.

Now inside that file, you can add a number of functions that are based on a number of events like loading or closing R. I need a .First function for on load and whatever I produce has to be able to print to the console with cat().

With that in mind, instead of showing details, I chose to show the number of breaches I’m in. You can get HIBPwned from CRAN and use it to query the awesome website HaveIBeenPwned.com.

I’ve seen people do things like this in .bash_profile, but didn’t know about .Rprofile before.

Mark Litwintschik has an ongoing taxi ride data analysis series.  This time, he gives PostgreSQL a run:

For this workload the reporting speeds don’t line up well with the price differences between the RDS instances. I suspect this workload is biased towards R’s CPU consumption when generating PNGs rather than RDS’ performance when returning aggregate results. The RDS instances share the same number of IOPS each which might erase any other performance advantage they could have over one another.

As for the money spent importing the data into RDS I suspect scaling up is more helpful when you have a number of concurrent users rather than a single, large job to execute.

This is an interesting series Mark has going.

Dan Goldstein gives a rule of thumb for getting standard deviations for various distributions:

Say you’ve got 30 numbers and a strong urge to estimate their standard deviation. But you’ve left your computer at home. Unless you’re really good at mentally squaring and summing, it’s pretty hard to compute a standard deviation in your head. But there’s a heuristic you can use:

Subtract the smallest number from the largest number and divide by four

Let’s call it the “range over four” heuristic. You could, and probably should, be skeptical. You could want to see how accurate the heuristic is. And you could want to see how the heuristic’s accuracy depends on the distribution of numbers you are dealing with.

Sometimes you just don’t have STDEV() available.

Alberto Giudici compares tidyr to reshape2 for data cleansing in R:

We see a different behaviour: gather() has brought messy into a long data format with a warning by treating all columns as variable, while melt() has treated trt as an “id variables”. Id columns are the columns that contain the identifier of the observation that is represented as a row in our data set. Indeed, if melt() does not receive any id.variables specification, then it will use the factor or character columns as id variables. gather() requires the columns that needs to be treated as ids, all the other columns are going to be used as key-value pairs.

Despite those last different results, we have seen that the two functions can be used to perform the exactly same operations on data frames, and only on data frames! Indeed, gather() cannot handle matrices or arrays, while melt() can as shown below.

It seems that these two tools have some overlap, but each has its own point of focus:  tidyr is simpler for data tidying, whereas reshape2 has functionality (like data aggregation) which tidyr does not include.

Hadley Wickham has a new version of tidyr out:

I’m pleased to announce tidyr 0.5.0. tidyr makes it easy to “tidy” your data, storing it in a consistent form so that it’s easy to manipulate, visualise and model. Tidy data has a simple convention: put variables in the columns and observations in the rows. You can learn more about it in the tidy data vignette.

Check out the latest version of tidyr; it’s one of the most useful data manipulation packages on the R platform.

Ginger Grant walks through how to fix a couple issues you might run into while installing SQL Server R Services:

If you look at the code from the interactive window, you will notice that the error occurred with trying to run rxSummary. In both cases I didn’t get the error when I changed the compute context to SQL Server from local, but when I tried to run a function which runs on the server. In both cases the R tools where installed prior to installing SQL Server 2016. The Open Source R tools install to C:\Program Files\R\R-3.3.0 (your version number may be higher). The Microsoft R Open installs to C:\Program Files\Microsoft\MRO\R-3.2.5. To use the libraries needed for the RevoScaleR libraries included in R Server, the version of Microsoft R required is Microsoft RRE, which is installed here C:\Program Files\Microsoft\MRO-for-RRE\8.0. Unfortunately, SQL Server 2016 shipped with version 8.0.3 not 8.0.0. If you are getting data and using a local compute context, you will have no problems. However, when you want to change your compute context to run on SQL Server, you will get an error.

While I received a different error on the server than my laptop, the reason for both messages was the same. Neither computer was running version 8.0.0.3 of the R client tools. On the server I was able to fix the error without downloading a thing. After installing a stand-alone version of R Server from the SQL Server Installation Center, the error went away and I got results when trying to run rxSummary. Unfortunately, it was not possible for me to run R Server on my laptop, as R Server is disabled from within the Installation Center. I believe that is because I have SQL Server 2016 developer edition on a laptop, not on a server. I needed to do something else to make it work.

Click the link for the full story.