How to convert coordinate columns to Point column with Shapely and Dask? - pandas

Question

I have the following problem. My data is a huge dataframe, looking like this (this is the head of the dataframe)
import pandas
import dask.dataframe as dd
data = dd.read_csv(data_path)
data.persist()
print(data.head())
Gitter_ID_100m x_mp_100m y_mp_100m Einwohner
0 100mN26840E43341 4334150 2684050 -1
1 100mN26840E43342 4334250 2684050 -1
2 100mN26840E43343 4334350 2684050 -1
3 100mN26840E43344 4334450 2684050 -1
4 100mN26840E43345 4334550 2684050 -1
I am using Dask to handle it. I now want to create a new column where the 'x_mp_100m' and 'y_mp_100m' are converted into a Shapely Point. For a single row, it would look like this:
from shapely.geometry import Point
test_df = data.head(1)
test_df = test_df.assign(geom=lambda k: Point(k.x_mp_100m,k.y_mp_100m))
print(test_df)
Gitter_ID_100m x_mp_100m y_mp_100m Einwohner geom
0 100mN26840E43341 4334150 2684050 -1 POINT (4334150 2684050)
I already tried the following code with Dask:
data_out = data.map_partitions(lambda df: df.assign(geom= lambda k: Point(k.x_mp_100m,k.y_mp_100m)), meta=pd.DataFrame)
When doing that, I get the following error:
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-17-b8de11d9b9b3> in <module>
----> 1 data_out.compute()
~\AppData\Local\Continuum\anaconda3\lib\site-packages\dask\base.py in compute(self, **kwargs)
154 dask.base.compute
155 """
--> 156 (result,) = compute(self, traverse=False, **kwargs)
157 return result
158
~\AppData\Local\Continuum\anaconda3\lib\site-packages\dask\base.py in compute(*args, **kwargs)
395 keys = [x.__dask_keys__() for x in collections]
396 postcomputes = [x.__dask_postcompute__() for x in collections]
--> 397 results = schedule(dsk, keys, **kwargs)
398 return repack([f(r, *a) for r, (f, a) in zip(results, postcomputes)])
399
~\AppData\Local\Continuum\anaconda3\lib\site-packages\distributed\client.py in get(self, dsk, keys, restrictions, loose_restrictions, resources, sync, asynchronous, direct, retries, priority, fifo_timeout, actors, **kwargs)
2319 try:
2320 results = self.gather(packed, asynchronous=asynchronous,
-> 2321 direct=direct)
2322 finally:
2323 for f in futures.values():
~\AppData\Local\Continuum\anaconda3\lib\site-packages\distributed\client.py in gather(self, futures, errors, maxsize, direct, asynchronous)
1653 return self.sync(self._gather, futures, errors=errors,
1654 direct=direct, local_worker=local_worker,
-> 1655 asynchronous=asynchronous)
1656
1657 #gen.coroutine
~\AppData\Local\Continuum\anaconda3\lib\site-packages\distributed\client.py in sync(self, func, *args, **kwargs)
671 return future
672 else:
--> 673 return sync(self.loop, func, *args, **kwargs)
674
675 def __repr__(self):
~\AppData\Local\Continuum\anaconda3\lib\site-packages\distributed\utils.py in sync(loop, func, *args, **kwargs)
275 e.wait(10)
276 if error[0]:
--> 277 six.reraise(*error[0])
278 else:
279 return result[0]
~\AppData\Local\Continuum\anaconda3\lib\site-packages\six.py in reraise(tp, value, tb)
691 if value.__traceback__ is not tb:
692 raise value.with_traceback(tb)
--> 693 raise value
694 finally:
695 value = None
~\AppData\Local\Continuum\anaconda3\lib\site-packages\distributed\utils.py in f()
260 if timeout is not None:
261 future = gen.with_timeout(timedelta(seconds=timeout), future)
--> 262 result[0] = yield future
263 except Exception as exc:
264 error[0] = sys.exc_info()
~\AppData\Local\Continuum\anaconda3\lib\site-packages\tornado\gen.py in run(self)
1131
1132 try:
-> 1133 value = future.result()
1134 except Exception:
1135 self.had_exception = True
~\AppData\Local\Continuum\anaconda3\lib\site-packages\tornado\gen.py in run(self)
1139 if exc_info is not None:
1140 try:
-> 1141 yielded = self.gen.throw(*exc_info)
1142 finally:
1143 # Break up a reference to itself
~\AppData\Local\Continuum\anaconda3\lib\site-packages\distributed\client.py in _gather(self, futures, errors, direct, local_worker)
1498 six.reraise(type(exception),
1499 exception,
-> 1500 traceback)
1501 if errors == 'skip':
1502 bad_keys.add(key)
~\AppData\Local\Continuum\anaconda3\lib\site-packages\six.py in reraise(tp, value, tb)
690 value = tp()
691 if value.__traceback__ is not tb:
--> 692 raise value.with_traceback(tb)
693 raise value
694 finally:
~\AppData\Local\Continuum\anaconda3\lib\site-packages\dask\dataframe\core.py in apply_and_enforce()
3682
3683 Ensures the output has the same columns, even if empty."""
-> 3684 df = func(*args, **kwargs)
3685 if isinstance(df, (pd.DataFrame, pd.Series, pd.Index)):
3686 if len(df) == 0:
<ipython-input-16-d5710cb00158> in <lambda>()
----> 1 data_out = data.map_partitions(lambda df: df.assign(geom= lambda k: Point(k.x_mp_100m,k.y_mp_100m)), meta=pd.DataFrame)
~\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\frame.py in assign()
3549 if PY36:
3550 for k, v in kwargs.items():
-> 3551 data[k] = com.apply_if_callable(v, data)
3552 else:
3553 # <= 3.5: do all calculations first...
~\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\common.py in apply_if_callable()
327
328 if callable(maybe_callable):
--> 329 return maybe_callable(obj, **kwargs)
330
331 return maybe_callable
<ipython-input-16-d5710cb00158> in <lambda>()
----> 1 data_out = data.map_partitions(lambda df: df.assign(geom= lambda k: Point(k.x_mp_100m,k.y_mp_100m)), meta=pd.DataFrame)
~\AppData\Local\Continuum\anaconda3\lib\site-packages\shapely\geometry\point.py in __init__()
47 BaseGeometry.__init__(self)
48 if len(args) > 0:
---> 49 self._set_coords(*args)
50
51 # Coordinate getters and setters
~\AppData\Local\Continuum\anaconda3\lib\site-packages\shapely\geometry\point.py in _set_coords()
130 self._geom, self._ndim = geos_point_from_py(args[0])
131 else:
--> 132 self._geom, self._ndim = geos_point_from_py(tuple(args))
133
134 coords = property(BaseGeometry._get_coords, _set_coords)
~\AppData\Local\Continuum\anaconda3\lib\site-packages\shapely\geometry\point.py in geos_point_from_py()
207 coords = ob
208 n = len(coords)
--> 209 dx = c_double(coords[0])
210 dy = c_double(coords[1])
211 dz = None
~\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\series.py in wrapper()
91 return converter(self.iloc[0])
92 raise TypeError("cannot convert the series to "
---> 93 "{0}".format(str(converter)))
94
95 wrapper.__name__ = "__{name}__".format(name=converter.__name__)
TypeError: cannot convert the series to <class 'float'>
So I think, I am using pandas.assign() function in a wrong way, or there should be a better fitting function, I just cannot seem to wrap my head around it. Do you know a better way to handle this?
I also found this way:
data_out = data.map_partitions(lambda df: df.apply(lambda row: Point(row['x_mp_100m'],row['y_mp_100m']), axis=1))
But is that the most efficient way?

Answer 1

What you're doing seems fine. I would find a function that works well on a single row and then use the apply method or a function that works well on a single Pandas dataframe and then use the map_partitions method.
For the error that you're getting I would first verify that your function works on a pandas dataframe.