"需要返回一个 pandas.Series, index 是股票代码,value 是因子值",我已经在cal函数里返回了一个type为<class 'pandas.core.series.Series'> ,index为股票代码,value为因子值的series,为什么会报错:only support single factor?
![TIM截图20180307172954.png][1]
![TIM截图20180307173105.png][2]
[1]: https://image.joinquant.net/26d0beb62f79a3fba9cff0b9292f1e10
[2]: https://image.joinquant.net/15b97d80abf4c442c0f36386ca50f1dc
2018-03-07