这是我数据框的头
date ,mkt.rf,smb,hml,rf
19990104,-0.0019,0.0021,0.0045,0.00019
19990105,0.011,-0.0088,0.0012,0.00019
19990106,0.021,-0.007,-0.004,0.00019
19990107,-7e-04,0.0046,-0.0022,0.00019
19990108,0.0045,-5e-04,0.0038,0.00019
您可以看到日期的结构不是日期格式，而是int格式。我没有尝试转换为日期格式，因为这对我来说也很复杂。我正在尝试从20180806到20180808提取信息。
我尝试了df$new_variable <- df[df$year == 20180806]。我很确定这是不完全正确的，而且我仍然缺少2个月
你能帮我做到这一点吗？
答案 0 :(得分：0)
我们可以使用subset中的base R
subset(df1, date >= 20180806 & date <=20180808)