JuliaLang/julia — Issue #470: NA/missing values
Author: HarlanH
Created: 2012-02-26 17:23:47+00:00
State: open

As discussed in [this thread](http://groups.google.com/group/julia-dev/browse_thread/thread/9f79ed4f8334830a), Julia needs to support data with missing values. Current thinking seems to be to create a parallel system of union types (e.g., IntData), promotion, and methods, rather than implementing anything at the bit level (which could be done, at least for floating point numbers). Note that [Matlab suggests overloading NaN for missing data](http://www.mathworks.com/help/techdoc/data_analysis/f0-10104.html), which is not a good idea, and [R uses NaN payload for floating NAs](https://svn.r-project.org/R/trunk/src/main/arithmetic.c).

References:
http://www.pauldickman.com/teaching/sas/missing.php
http://cran.r-project.org/doc/manuals/R-lang.pdf (section 3.3.4)