Support column rolling? about dataframe

[hosseinmoein]

@yssource
You could write a simple functor and use one of the visit() or single_act_visit() methods to get this result.
But I can add something specialized maybe in the next few days or so

[hosseinmoein]

@yssource
I implemented the SimpleRollAdptor. It works with most of the visitors.
Please see the doc and data_frame_tester.cc for usage

[yssource]

It seems that the NaN is not considered.

std::vector<double> d1 = {1, 2, 3, 4, 
// 5, 
std::numeric_limits<double>::quiet_NaN(), 
6,
 // 7, 
std::numeric_limits<double>::quiet_NaN(), 
8, 9, 10, 11};

#+begin_src python :results output
  import numpy as np
  import pandas as pd

  x = np.array([0, 1, 2, 3, np.nan, 5, 6, 7, 8, np.nan, 10])
  s = pd.Series(x)

  print(s.rolling(3).min())
  print(s.rolling(3).max())
  print(s.rolling(3).mean())
  print(s.rolling(3).std())
#+end_src

#+RESULTS:
#+begin_example
0     NaN
1     NaN
2     0.0
3     1.0
4     NaN
5     NaN
6     NaN
7     5.0
8     6.0
9     NaN
10    NaN
dtype: float64
0     NaN
1     NaN
2     2.0
3     3.0
4     NaN
5     NaN
6     NaN
7     7.0
8     8.0
9     NaN
10    NaN
dtype: float64
0     NaN
1     NaN
2     1.0
3     2.0
4     NaN
5     NaN
6     NaN
7     6.0
8     7.0
9     NaN
10    NaN
dtype: float64
0     NaN
1     NaN
2     1.0
3     1.0
4     NaN
5     NaN
6     NaN
7     1.0
8     1.0
9     NaN
10    NaN
dtype: float64
#+end_example

[hosseinmoein]

That is because my generic visitors, like min, max, mean, etc., skip nans. I should make it optional.

[hosseinmoein]

@yssource
Made skipping nans optional in visitors. The default is still to skip nans.
See the tester file and docs

[yssource]

It works as expected.
Thank you, so much.