说明:本文章为Python数据处理学习日志,记录内容为实现书本内容时遇到的错误以及一些与书本不一致的地方,一些简单操作则不再赘述。日志主要内容来自书本《利用Python进行数据分析》,Wes McKinney著,机械工业出版社。
3、分组级运算和转换
P285示例
pct_change()
Signature: DataFrame.pct_change(self, periods=1, fill_method=’pad’, limit=None, freq=None, **kwargs)
Docstring Percent change over given number of periods.
Parameters
periods : int, default 1
Periods to shift for forming percent change
fill_method : str, default ‘pad’
How to handle NAs before computing percent changes
limit : int, default None
The number of consecutive NAs to fill before stopping
freq : DateOffset, timedelta, or offset alias string, optional
Increment to use from time series API (e.g. ‘M’ or BDay())
Returns
chg : NDFrame
这个函数运算方法如下:
test = DataFrame([,,,,])
test['pct_change'] = test.pct_change()
test
Out[]:
pct_change
NaN #第一个数据没有
#(2-1)/1=1
#(4-2)/2=1
#(4-4)/4=0
#(5-4)/4=0
test['pct_change'] = test.pct_change(periods=)
test
Out[]:
pct_change
NaN
NaN #前两个没有
#(4-1)/1=3
#(4-2)/2=1
#(5-4)/4=0.25