la 0.3

Label the rows, columns, any dimension, of your NumPy arrays.

The main class of the la package is a labeled array, larry. A larry consists of data and labels. The data is stored as a NumPy array and the labels as a list of lists (one list per dimension).

Here’s larry in schematic form:

             date1    date2    date3
    'AAPL'   209.19   207.87   210.11
y = 'IBM'    129.03   130.39   130.55
    'DELL'    14.82    15.11    14.94

The larry above is stored internally as a Numpy array and a list of lists:

y.label = [['AAPL', 'IBM', 'DELL'], [date1, date2, date3]]
y.x = np.array([[209.19, 207.87, 210.11],
                [129.03, 130.39, 130.55],
                [ 14.82,  15.11,  14.94]])

A larry can have any number of dimensions except zero. Here, for example, is one way to create a one-dimensional larry:

>>> import la
>>> y = la.larry([1, 2, 3])

In the statement above the list is converted to a Numpy array and the labels default to range(n), where n in this case is 3.

larry has built-in methods such as movingsum, ranking, merge, shuffle, zscore, demean, lag as well as typical Numpy methods like sum, max, std, sign, clip. NaNs are treated as missing data.

Alignment by label is automatic when you add (or subtract, multiply, divide) two larrys.

You can archive larrys in HDF5 format using save and load or using a dictionary-like interface:

>>> io = la.IO('/tmp/dataset.hdf5')
>>> io['y'] = y   # <--- save
>>> z = io['y']   # <--- load
>>> del io['y']   # <--- delete from archive

For the most part larry acts like a Numpy array. And, whenever you want, you have direct access to the Numpy array that holds your data. For example if you have a function, myfunc, that works on Numpy arrays and doesn’t change the shape or ordering of the array, then you can use it on a larry, y, like this:

y.x = myfunc(y.x)

larry adds the convenience of labels, provides many built-in methods, and let’s you use your existing array functions.

docs	http://berkeleyanalytics.com/la
code	http://github.com/kwgoodman/la
issues	http://github.com/kwgoodman/la/issues
list	http://groups.google.com/group/labeled-array

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