我想在Jupyter Notebook中使用ggplot2。但是，当我尝试制作 R 魔术单元并引入变量时，出现错误。
这是代码(一个段落表示一个单元格(：
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns
import rpy2
%matplotlib inline
from rpy2.robjects import pandas2ri
pandas2ri.activate()
%load_ext rpy2.ipython
%%R
library(ggplot2)
data = pd.read_csv('train_titanic.csv')
%%R -i data -w 900 -h 480 -u px
使用最后一个单元格，我得到以下错误(包括回溯(：
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/robjects/pandas2ri.py in py2rpy_pandasdataframe(obj)
54 try:
---> 55 od[name] = conversion.py2rpy(values)
56 except Exception as e:
~/anaconda3/envs/catenv/lib/python3.7/functools.py in wrapper(*args, **kw)
839
--> 840 return dispatch(args[0].__class__)(*args, **kw)
841
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/robjects/pandas2ri.py in py2rpy_pandasseries(obj)
125 if type(x) is not homogeneous_type:
--> 126 raise ValueError('Series can only be of one type, or None.')
127 # TODO: Could this be merged with obj.type.name == 'O' case above ?
ValueError: Series can only be of one type, or None.
During handling of the above exception, another exception occurred:
TypeError Traceback (most recent call last)
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/rinterface_lib/sexp.py in from_object(cls, obj)
367 try:
--> 368 mv = memoryview(obj)
369 res = cls.from_memoryview(mv)
TypeError: memoryview: a bytes-like object is required, not 'Series'
During handling of the above exception, another exception occurred:
AttributeError Traceback (most recent call last)
<ipython-input-14-75e210679e4a> in <module>
----> 1 get_ipython().run_cell_magic('R', '-i data -w 900 -h 480 -u px', 'nn')
~/anaconda3/envs/catenv/lib/python3.7/site-packages/IPython/core/interactiveshell.py in run_cell_magic(self, magic_name, line, cell)
2360 with self.builtin_trap:
2361 args = (magic_arg_s, cell)
-> 2362 result = fn(*args, **kwargs)
2363 return result
2364
</home/morgan/anaconda3/envs/catenv/lib/python3.7/site-packages/decorator.py:decorator-gen-130> in R(self, line, cell, local_ns)
~/anaconda3/envs/catenv/lib/python3.7/site-packages/IPython/core/magic.py in <lambda>(f, *a, **k)
185 # but it's overkill for just that one bit of state.
186 def magic_deco(arg):
--> 187 call = lambda f, *a, **k: f(*a, **k)
188
189 if callable(arg):
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/ipython/rmagic.py in R(self, line, cell, local_ns)
721 raise NameError("name '%s' is not defined" % input)
722 with localconverter(converter) as cv:
--> 723 ro.r.assign(input, val)
724
725 tmpd = self.setup_graphics(args)
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/robjects/functions.py in __call__(self, *args, **kwargs)
190 kwargs[r_k] = v
191 return (super(SignatureTranslatedFunction, self)
--> 192 .__call__(*args, **kwargs))
193
194
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/robjects/functions.py in __call__(self, *args, **kwargs)
111
112 def __call__(self, *args, **kwargs):
--> 113 new_args = [conversion.py2rpy(a) for a in args]
114 new_kwargs = {}
115 for k, v in kwargs.items():
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/robjects/functions.py in <listcomp>(.0)
111
112 def __call__(self, *args, **kwargs):
--> 113 new_args = [conversion.py2rpy(a) for a in args]
114 new_kwargs = {}
115 for k, v in kwargs.items():
~/anaconda3/envs/catenv/lib/python3.7/functools.py in wrapper(*args, **kw)
838 '1 positional argument')
839
--> 840 return dispatch(args[0].__class__)(*args, **kw)
841
842 funcname = getattr(func, '__name__', 'singledispatch function')
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/robjects/pandas2ri.py in py2rpy_pandasdataframe(obj)
59 'The error is: %s'
60 % (name, str(e)))
---> 61 od[name] = StrVector(values)
62
63 return DataFrame(od)
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/robjects/vectors.py in __init__(self, obj)
382
383 def __init__(self, obj):
--> 384 super().__init__(obj)
385 self._add_rops()
386
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/rinterface_lib/sexp.py in __init__(self, obj)
286 super().__init__(obj)
287 elif isinstance(obj, collections.abc.Sized):
--> 288 super().__init__(type(self).from_object(obj).__sexp__)
289 else:
290 raise TypeError('The constructor must be called '
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/rinterface_lib/sexp.py in from_object(cls, obj)
370 except (TypeError, ValueError):
371 try:
--> 372 res = cls.from_iterable(obj)
373 except ValueError:
374 msg = ('The class methods from_memoryview() and '
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/rinterface_lib/conversion.py in _(*args, **kwargs)
26 def _cdata_res_to_rinterface(function):
27 def _(*args, **kwargs):
---> 28 cdata = function(*args, **kwargs)
29 # TODO: test cdata is of the expected CType
30 return _cdata_to_rinterface(cdata)
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/rinterface_lib/sexp.py in from_iterable(cls, iterable, populate_func)
317 if populate_func is None:
318 cls._populate_r_vector(iterable,
--> 319 r_vector)
320 else:
321 populate_func(iterable, r_vector)
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/rinterface_lib/sexp.py in _populate_r_vector(cls, iterable, r_vector)
300 r_vector,
301 cls._R_SET_VECTOR_ELT,
--> 302 cls._CAST_IN)
303
304 @classmethod
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/rinterface_lib/sexp.py in _populate_r_vector(iterable, r_vector, set_elt, cast_value)
237 def _populate_r_vector(iterable, r_vector, set_elt, cast_value):
238 for i, v in enumerate(iterable):
--> 239 set_elt(r_vector, i, cast_value(v))
240
241
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/rinterface_lib/sexp.py in _as_charsxp_cdata(x)
430 return x.__sexp__._cdata
431 else:
--> 432 return conversion._str_to_charsxp(x)
433
434
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/rinterface_lib/conversion.py in _str_to_charsxp(val)
118 s = rlib.R_NaString
119 else:
--> 120 cchar = _str_to_cchar(val)
121 s = rlib.Rf_mkCharCE(cchar, _CE_UTF8)
122 return s
~/anaconda3/envs/catenv/lib/python3.7/site-packages/rpy2/rinterface_lib/conversion.py in _str_to_cchar(s, encoding)
97 def _str_to_cchar(s, encoding: str = 'utf-8'):
98 # TODO: use isStrinb and installTrChar
---> 99 b = s.encode(encoding)
100 return ffi.new('char[]', b)
101
AttributeError: 'float' object has no attribute 'encode'
所以我发现在导入我的熊猫数据帧对象时甚至无法启动 R 魔术单元。但是，我尝试在单元格内创建 R 向量，发现我可以毫无问题地使用ggplot2绘制这些向量。
我正在使用Python 3.7.6，rpy2 3.1.0，jupyter-notebook 6.0.3，并且正在Linux的Windows子系统上使用Ubuntu 18.04.2 LTS。
问题很可能是一列(或多列(具有多种类型 - 因此不可能将数据传输到 R 向量(只能容纳一种数据类型(。回溯可能是压倒性的，但这是相关的部分：
ValueError: Series can only be of one type, or None.
这是哪一列？如果不查看您加载的数据集，很难说，但我的一般解决方案是检查列中的类型：
types = data.applymap(type).apply(set)
types[types.apply(len) > 1]
上面代码段返回的任何内容都将是候选罪魁祸首。有许多不同的方法来处理这个问题，具体取决于数据的确切性质。我经常使用的解决方法包括：
- 调用
data = data.infer_objects()- 如果熊猫没有赶上 dtype 更改并且仍然使用(次优(Python 对象存储数据会有所帮助 - 如果字符串列中有缺失值，则用空字符串或字符串常量填充
NaN(例如str_columns = str_columns.fillna('')( dates.apply(pd.to_datetime, axis=1)如果您有datetime对象，但 dtype 是对象- 如果混合了
date对象和datetime对象，请使用df.applymap(lambda x: datetime.combine(x, datetime.min.time()) if not isinstance(x, datetime) else x)
在某些罕见的情况下，pandas 存储的数据与 rpy2 的预期不同(遵循某些操作(;然后将数据帧写入 csv 文件并再次从磁盘读取它会有所帮助 - 但这可能不是你在这里面对的，因为你从新读取的数据帧开始。
我只是注意到这个问题可能有一个更简单的原因。出于某种原因，pandas2ri要求您在导入后调用pandas2ri.activate()。这为我解决了问题。