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pythonrrpy2r-maptools

R maptools wrld_simpl in rpy2

In R:

import(maptools)
data(wrld_simpl)

In python rpy2, how do I access wrld_simpl? The following code (in Python) fails as follows...package "maptools" has no attribute wrld_simpl

maptools = importr('maptools')
data = DataFrame(maptools.wrld_simpl)

Just trying to understand rpy2 (and revisit R from university days)

Solution

  • Use rpy2.robjects.packages.data, as demonstrated in the rpy2 introduction:

    >>> from rpy2.robjects.packages import importr, data

>>> maptools = importr('maptools')
>>> spatial_df_r = data(maptools).fetch('wrld_simpl')['wrld_simpl']
>>> spatial_df_r
<rpy2.robjects.methods.RS4 object at 0x7ffa932b0cc0> [RTYPES.S4SXP]
R classes: ('SpatialPolygonsDataFrame',)

    You also seem to be trying to convert the data to pandas.DataFrame. The slight issue is that the data is not a data frame, but a SpatialPolygonsDataFrame object. You can however convert it to a proper data.frame:

    >>> base = importr('base')
>>> df_r = base.as_data_frame(spatial_df_r)
>>> tuple(df_r.rclass)
('data.frame',)

    and then to pandas DataFrame:

    from rpy2.robjects import conversion
from rpy2.robjects import default_converter, pandas2ri

with conversion.localconverter(default_converter + pandas2ri.converter):
    df = conversion.rpy2py(df_r)

    where df is now a pandas DataFrame:

    >>> type(df)
<class 'pandas.core.frame.DataFrame'>

    However, if you are using Jupyter, the conversion can be done much more easily with with -o option of rpy2 magic, see: using rpy2 in notebooks and rpy2.ipython.rmagic.