技術標籤：Pandas基礎numpymatlabpythonpandas

cumsum是matlab中一個函式，通常用於計算一個數組各行的累加值

# 使用累積求和cumsum() nan會被忽略
s = pd.Series([2, np.nan, 5, -1, 0])
s
'''
0    2.0
1    NaN
2    5.0
3   -1.0
4    0.0
dtype: float64

'''

s.cumsum() #按列相加
'''
0    2.0
1    NaN
2    7.0
3    6.0
4    6.0
dtype: float64
'''

df = pd.DataFrame([[2.0, 1.0],[3.0, np.nan],[1.0, 0.0]],columns=list('AB'))

df
	A	B
0	2.0	1.0
1	3.0	NaN
2	1.0	0.0

df.cumsum() # 按列相加
	A	B
0	2.0	1.0
1	5.0	NaN
2	6.0	1.0

df.cumsum(axis=1) # 按行相加

A	B
0	2.0	3.0
1	3.0	NaN
2	1.0	1.0