Bad Data


I just finished reading the Bad Data Handbook, edited by Q. Ethan McCallum (O'Reilly, 2013). This is a nice book with interesting chapters on data munging and data verification.

Among the authors, you will find a long list of well-known statisticians and data hackers: Paul Murrell (besides R extensions to the grid package, he authored Introduction to Data Technologies), Richard Cotton (4D Pie CHarts), or Philipp K Janert, who wrote Data Analysis with Open Source Tools (O’Reilly, 2010), another great handbook on applied statistics using GNU software.

While Kevin Fink (Chapter 1, "Is It Just Me, or Does This Data Smell Funny?") provided Perl code exclusively, I had the pleasure to read beautiful Python snippets from Josh Levy's chapter ("Bad Data Lurking in Plain Text"), and a nice historical sketch of text encoding starting with 7-bit ASCII encoding to Unicode (UTF-8 and 16). This also reminded me of how dealing with various charsets (including Windows CP 1252) really sucks in R, while Stata is not that good when it comes to UTF-8; so the solution to normalize data to UTF-8 is not necessarily the penultimate solution, but it will probably help. Please, everybody, use UTF-8 now! There's a small utility called iconv that is really great for that purpose.

When reading Paul Murrell's chapter, "Data Intended for Human Consumption, Not Machine Consumption", I discovered the XLConnect R package to read Excel spreadsheets directly in R instead of relying on intermediate CSV file.(a) Now that I know that sometimes it is better to read data directly from Excel, the technique described by the author to extract and process data formatted in several 'non-regular' Excel Tables (of course, this assumes that such custom layout applies to all Tables), I will probably consider working with Excel files directly for my next project (yeah, that seems to the year where all the databases I have to work on are provided to me as freak Excel spreadsheets).


(a) See also A million ways to connect R and Excel for an overview of other packages.


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