Re: [Matplotlib-users] record array and date support

[John H. <jd...@gm...>]

On 6/8/07, Lionel Roubeyrie <lro...@li...> wrote:
> Hi John,
> very very interesting idea.
> Is there a way to add some extras informations on the records arrays columns,
> like the units or/and the desired labels for the resulting plotted lines,
> directly retrieved in the CSV files?

It could be done, but my goal here is not to create a persistence
layer for record arrays, or a method of describing them or mpl labels,
but rather a way to easily import 3rd party CSV files into numpy
record arrays.  I work with a lot of tab/space/ascii delimited files,
and found myself duplicating a lot of code importing them into record
arrays.  This function is the distillation of that code.  It would be
fairly easy to add designated rows for those who did want to decorate
their CSV files.  I think it might be most useful to support a row
that provided a numpy dtype per column, or perhaps the name of a
converter function...

One thing people coming from gnuplot miss is file plotting
functionality.  I just added a function to pylab called plotfile which
uses the csv2rec functionality (with autolabeling etc) to plot data
from a file.  Eg,

>>> plotfile(fname, (0,5,6))

plots columns 5 and 6 against column 0.  And

>>> plotfile(fname, ('date', 'volume', 'adj_close'),
plotfuncs={'volume': 'bar'})

does the same using the names of the columns, using "plot" for
adj_close (the default) and "bar" for volume (customization from the
plotfuncs dictionary).  The column names in either case are used to
create default x and y labels.

The 2nd command produces the attached plot.  This is just a first
pass, so if people want to see a different interface or have an
opinion what should be returned, or where this function should live
outside of pylab, feel free to comment or commit changes.

JDH