I was reading about the Julia dataframe implementation yesterday,
trying to understand their decisions and how D might implement.
From my notes,
1. they are currently using a dictionary of column vectors.
2. for NA (not available) they are currently using an array of
bytes, effectively as a Boolean flag, rather than a bitVector,
for performance reasons.
3. they are not currently implementing hierarchical headers.
4. they are transforming non-valid symbol header strings (read
from csv, for example) to valid symbols by replacing '.' with
underscore and prefixing numbers with 'x', as examples. This
allows use in expressions.
5. Along with 4., they currently have @with for DataVector, to
allow expressions to use, for example, :symbol_name instead of
dv[:symbol_name].
6. They have operation symbols for per element operations on two
vectors, for example a ./ b expresses applying the operation to
the vector.
7. They currently only have row indexes, no row names or symbols.
I saw someone posting that they were working on DataFrame
implementation here, but haven't been able to locate any code in
github, and was wondering what implementation decisions are being
made here. Thanks.
