计算上面行的平方和

问题描述

我有一个数据集，如下所示：

Value         Type       X_sq
-1.975767     Weather   
-0.540979     Fruits
-2.359127     Fruits
-2.815604     Corona
-0.929755     Weather

我想遍历每一行，并计算上面每一行的平方和(仅当Type匹配时)。我想将此值放在X.sq列中。

例如，在第一行，上面没有任何东西。仅如此(-1.975767 x-1.975767)。在第二行中，它的上方没有水果行，所以它将是-0.540979 x-0.540979。然而，在第三行中，当我们扫描前面的所有行时，我们应该发现水果已经在那里了。所以我们应该吃最后一颗果子……X_sq值并计算新的平方和。

Value         Type       X_sq
-1.975767     Weather   -1.975767 * -1.975767    = x
-0.540979     Fruits    -0.540979 * -0.540979    = y
-2.359127     Fruits    y + ( -2.359127 x -2.359127)  
-2.815604     Corona    -2.815604 * -2.815604
-0.929755     Weather   x + (-0.929755 * -0.929755)

执行此操作的有效方法是什么？

def updateSS(X_sq, X_new):
    return X_sq + X_new**2

编辑：

----> 1 df['sumOfSquares'] = df['avg_country_tone'].pow(2).groupby(['themes', 'suppliers_country']).cumsum()
     

File /usr/local/Cellar/ipython/8.0.1/libexec/lib/python3.10/site-packages/pandas/core/series.py:1929, in Series.groupby(self, by, axis, level, as_index, sort, group_keys, squeeze, observed, dropna)
   1925 axis = self._get_axis_number(axis)
   1927 # error: Argument "squeeze" to "SeriesGroupBy" has incompatible type
   1928 # "Union[bool, NoDefault]"; expected "bool"
-> 1929 return SeriesGroupBy(
   1930     obj=self,
   1931     keys=by,
   1932     axis=axis,
   1933     level=level,
   1934     as_index=as_index,
   1935     sort=sort,
   1936     group_keys=group_keys,
   1937     squeeze=squeeze,  # type: ignore[arg-type]
   1938     observed=observed,
   1939     dropna=dropna,
   1940 )

File /usr/local/Cellar/ipython/8.0.1/libexec/lib/python3.10/site-packages/pandas/core/groupby/groupby.py:882, in GroupBy.__init__(self, obj, keys, axis, level, grouper, exclusions, selection, as_index, sort, group_keys, squeeze, observed, mutated, dropna)
    879 if grouper is None:
    880     from pandas.core.groupby.grouper import get_grouper
--> 882     grouper, exclusions, obj = get_grouper(
    883         obj,
    884         keys,
    885         axis=axis,
    886         level=level,
    887         sort=sort,
    888         observed=observed,
    889         mutated=self.mutated,
    890         dropna=self.dropna,
    891     )
    893 self.obj = obj
    894 self.axis = obj._get_axis_number(axis)

File /usr/local/Cellar/ipython/8.0.1/libexec/lib/python3.10/site-packages/pandas/core/groupby/grouper.py:882, in get_grouper(obj, key, axis, level, sort, observed, mutated, validate, dropna)
    880         in_axis, level, gpr = False, gpr, None
    881     else:
--> 882         raise KeyError(gpr)
    883 elif isinstance(gpr, Grouper) and gpr.key is not None:
    884     # Add key to exclusions
    885     exclusions.add(gpr.key)

KeyError: 'themes'
even though themes is there. Themes = type

---

解决方案

使用：

df['X_sq'] = df['Value'].pow(2).groupby(df['Type']).cumsum()
print(df)

# Output
      Value     Type      X_sq
0 -1.975767  Weather  3.903655
1 -0.540979   Fruits  0.292658
2 -2.359127   Fruits  5.858138
3 -2.815604   Corona  7.927626
4 -0.929755  Weather  4.768100