Exclude center value from centered rolling average in Pandas

I want to calculate the centered rolling average in Pandas, where the center value is excluded.

The code below works perfectly, but it includes the center value:

df.Value.rolling(window=11, center=True, min_periods=1).mean()

The window=11 and min_periods=1 are important, since I want to calculate the average for every value in df.

For example,

• for the second value, it should consider 5 values below and 1 that is above the current value. (Current code includes the second value)
• for the last value, it should consider 5 values above, but exclude the last one. (Current code considers the last 6 values)

Here is a table with the expected results:

And calculation method from Excel:

Example Table

updated answer

You can modify my first approach of the initial answer to have a dynamic division:

win = 11
roll = df['Values'].rolling(window=win, center=True, min_periods=1)

df['out'] = roll.sum().sub(df['Values']).div(roll.count()-1)

Output:

    Values     Expected           out
0    13313  27180.60000  27180.600000
1    12792  28897.00000  28897.000000
2    20254  28770.14286  28770.142857
3    34915  27468.50000  27468.500000
4    31410  29037.00000  29037.000000
5    36532  30028.50000  30028.500000
6    36958  34071.10000  34071.100000
7    35471  36600.66667  36600.666667
8    33018  38950.62500  38950.625000
9    38080  38804.00000  38804.000000
10   44074  39037.33333  39037.333333
11   54165  37520.20000  37520.200000

initial answer

You have different ways, whether or not the operation is really a mean:

np.random.seed(0)
df = pd.DataFrame({'Value': np.random.randint(0, 10, 10)})

win = 3

df['mean'] = df['Value'].rolling(window=win, center=True, min_periods=1).mean()

df['mean_without_center'] = (df['Value'].rolling(window=win, center=True, min_periods=1)
                             .sum().sub(df['Value']).div(win-1)
                            )

half = win//2
mask = [False]*half+[True]+[False]*half

df['mean_without_center_apply'] = (df['Value'].rolling(window=win, center=True, min_periods=1)
                             .apply(lambda s: s.mask(mask[:len(s)]).mean())
                            )

Output:

   Value      mean  mean_without_center  mean_without_center_apply
0      5  2.500000                  0.0                        5.0
1      0  2.666667                  4.0                        4.0
2      3  2.000000                  1.5                        1.5
3      3  4.333333                  5.0                        5.0
4      7  6.333333                  6.0                        6.0
5      9  6.333333                  5.0                        5.0
6      3  5.666667                  7.0                        7.0
7      5  3.333333                  2.5                        2.5
8      2  3.666667                  4.5                        4.5
9      4  3.000000                  1.0                        2.0

Or with [tag:numpy]'s sliding_window_view:

from numpy.lib.stride_tricks import sliding_window_view as swv

win = 3
half = win//2

df['swv_mean'] = np.nanmean(swv(np.pad(df['Value'].astype(float), (win-1, 0),
                                       constant_values=np.nan),
                                win)
                            [:, np.r_[:half, half+1:win]],
                            axis=1
                           )

Output:

   Value  swv_mean
0      5       5.0
1      0       0.0
2      3       4.0
3      3       1.5
4      7       5.0
5      9       6.0
6      3       5.0
7      5       7.0
8      2       2.5
9      4       4.5