Any practicing data scientist is going to eventually have to work with a data stored in a Microsoft Excel spreadsheet. A lot of analysts use this format, so if you work with others you are going to run into it. We have already written how we don’t recommend using Excel-like formats to exchange data. But we know if you are going to work with others you are going to have to make accommodations (we even built our own modified version of gdata‘s underlying Perl script to work around a bug).
But one thing that continues to confound us is how hard it is to read Excel data correctly. When Excel exports into CSV/TSV style formats it uses fairly clever escaping rules about quotes and new-lines. Most CSV/TSV readers fail to correctly implement these rules and often fail on fields that contain actual quote characters, separators (tab or comma), or new-lines. Another issue is Excel itself often transforms data without any user verification or control. For example: Excel routinely turns date-like strings into time since epoch (which it then renders as a date). We recently ran into another uncontrollable Excel transform: changing the strings “TRUE” and “FALSE” into 1 and 0 inside the actual “.xlsx” file. That is Excel does not faithfully store the strings “TRUE” and “FALSE” even in its native format. Most Excel users do not know about this, so they certainly are in no position to warn you about it.
This would be a mere annoyance, except it turns out Libre Office (or at least LibreOffice_4.3.4_MacOS_x86-64) has a severe and silent data mangling bug on this surprising Microsoft boolean type.
We first ran into this in client data (and once the bug triggered it seemed to alter most of the columns), but it turns out the bug is very easy to trigger. In this note we will demonstrate the data representation issue and bug. Continue reading Excel spreadsheets are hard to get right
Having worked with Unix (BSD, HPUX, IRIX, Linux and OSX), Windows (NT4, 2000, XP, Vista and 7) for quite a while I have seen a lot of different software tools. I would like to quickly exhibit my “must have” list. These are the packages that I find to be the single “must have offerings” in a number of categories. I have avoided some categories (such as editors, email programs, programing language, IDEs, photo editors, backup solutions, databases, database tools and web tools) where I have no feeling of having seen a single absolute best offering.
The spirit of the list is to pick items such that: if you disagree with an item in this list then either you are wrong or you know something I would really like to hear about.