[英]How do I groupby a dataframe based on values that are common to multiple columns?
I am trying to aggregate a dataframe based on values that are found in two columns. 我试图基于在两列中找到的值聚合一个数据框。 I am trying to aggregate the dataframe such that the rows that have some value X in either column A or column B are aggregated together.
我正在尝试聚合数据帧,以使在A列或B列中具有某些值X的行聚合在一起。
More concretely, I am trying to do something like this. 更具体地说,我正在尝试做这样的事情。 Let's say I have a dataframe gameStats:
假设我有一个dataframe gameStats:
awayTeam homeTeam awayGoals homeGoals
Chelsea Barca 1 2
R. Madrid Barca 2 5
Barca Valencia 2 2
Barca Sevilla 1 0
... and so on ... 等等
I want to construct a dataframe such that among my rows I would have something like: 我想构造一个数据框,以使我的行中有类似以下内容的内容:
team goalsFor goalsAgainst
Barca 10 5
One obvious solution, since the set of unique elements is small, is something like this: 一个显而易见的解决方案是,因为唯一元素的集合很小,所以它是这样的:
for team in teamList:
aggregateDf = gameStats[(gameStats['homeTeam'] == team) | (gameStats['awayTeam'] == team)]
# do other manipulations of the data then append it to a final dataframe
However, going through a loop seems less elegant. 但是,经历循环似乎不太优雅。 And since I have had this problem before with many unique identifiers, I was wondering if there was a way to do this without using a loop as that seems very inefficient to me.
而且由于我以前使用很多唯一标识符遇到了这个问题,所以我想知道是否有一种方法可以不使用循环,因为这对我来说似乎效率很低。
The solution is 2 folds, first compute goals for each team when they are home and away, then combine them. 解决方案是2折,首先为每个团队在出差时计算目标,然后将它们组合起来。 Something like:
就像是:
goals_when_away = gameStats.groupby(['awayTeam'])['awayGoals', 'homeGoals'].agg('sum').reset_index().sort_values('awayTeam')
goals_when_home = gameStats.groupby(['homeTeam'])['homeGoals', 'awayGoals'].agg('sum').reset_index().sort_values('homeTeam')
then combine them 然后结合起来
np_result = goals_when_away.iloc[:, 1:].values + goals_when_home.iloc[:, 1:].values
pd_result = pd.DataFrame(np_result, columns=['goal_for', 'goal_against'])
result = pd.concat([goals_when_away.iloc[:, :1], pd_result], axis=1, ignore_index=True)
Note .values
when summing to get result in numpy array, and ignore_index=True
when concat, these are to avoid pandas trap when it sums by column and index names. 注意在
.values
以在numpy数组中获取结果时使用.values
,在concat时请使用ignore_index=True
,这是为了避免在按列名和索引名求和时出现大熊猫陷阱。
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