[英]Creating a histogram for each value in multi-index pandas dataframe
Below is a small section from my pandas dataframe. 以下是我的熊猫数据框的一小部分。 I would like to be able to get separate 'vel_x' histograms (counts, bins) for each value in count.
我希望能够为计数中的每个值获得单独的“ vel_x”直方图(计数,箱)。 Is there a fast, built-in way to do this without just looping through each value in count?
是否有一种快速的内置方法来执行此操作,而不仅仅是循环遍历每个计数值?
+-------+-------+-------+-------+--------+----+--------+
| | | x_loc | y_loc | vel_x | … | vel_z |
+-------+-------+-------+-------+--------+----+--------+
| count | slice | | | | | |
| 1 | 3 | 4 | 0 | 96 | 88 | 35 |
| | 4 | 10 | 2 | 54 | 42 | 37 |
| | 5 | 9 | 32 | 8 | 70 | 34 |
| | 6 | 36 | 89 | 69 | 46 | 78 |
| 2 | 5 | 17 | 41 | 48 | 45 | 71 |
| | 6 | 50 | 66 | 82 | 72 | 59 |
| | 7 | 14 | 24 | 55 | 20 | 89 |
| | 8 | 76 | 36 | 13 | 14 | 21 |
| 3 | 5 | 97 | 19 | 41 | 61 | 72 |
| | 6 | 22 | 4 | 56 | 82 | 15 |
| | 7 | 17 | 57 | 30 | 63 | 88 |
| | 8 | 83 | 43 | 35 | 8 | 4 |
+-------+-------+-------+-------+--------+----+--------+
I have tried many methods (apply, map, etc.), but I have not been able to get any of them to work. 我尝试了许多方法(应用,地图等),但是我无法使它们中的任何一个起作用。 Each method just applies the mapped function to all the row values.
每种方法仅将映射函数应用于所有行值。
Essentially, I want to map this to each value in count (count_value) below: 本质上,我想将此映射到下面的count(count_value)个值中:
def create_histogram(data, count_value):
values, bin_edges = np.histogram(data.loc[count_value, 'vel_x'])
return values
then something like this: 然后是这样的:
data.index.get_level_values('Count').map(create_histrogram(data))
Also, for reference, this is the way I can currently perform what I want, but it is not very efficient because my dataframe is very large. 另外,作为参考,这是我当前可以执行所需操作的方式,但是效率不高,因为我的数据帧非常大。
for count_value in data.index.get_level_values('Count').unique:
values, bin_edges = np.histogram(data.loc[count_value, 'vel_x'])
the returned values can then be stored in another array. 然后可以将返回的值存储在另一个数组中。
Thank you in advance for your help! 预先感谢您的帮助!
How about using groupby with level
param: 如何将groupby与
level
参数一起使用:
level : int, level name, or sequence of such, default None If the axis is a MultiIndex (hierarchical), group by a particular level or levels
level:int,级别名称或此类的序列,默认值无如果轴是MultiIndex(分层),则按一个或多个特定级别分组
for count, sdf in df.groupby(level=0):
values, bin_edges = np.histogram(sdf.loc[count, 'vel_x'])
UPDATE 更新
Since you think the way mean(level=level)
works is better, you can also try this way which is inspired by mean
source code : 由于您认为
mean(level=level)
工作方式更好,因此您也可以尝试以下这种方法,这种方法受mean
源代码的启发:
df['vel_x'].groupby(level=0).aggregate(np.histogram)
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.