两年值之间的比率

Question

我有一个带有值列和相应年份的数据框。我想创建一个额外的列，其中应包含以5年为间隔的年份的价值比率，向后倒退。例如 如果年份是2000，则'newval'列应具有2000和1995年的值比率。我的数据框如下所示。可能缺少年份，并且“值”和“年份”列中都没有数据。

df2 = data.frame(code = c("AFG", "AGO", "ALB", "AND", "ARB", "ARE", "ARG", "ARM", "ASM", "ATG", "AUS", "AUT","AUT"),
            val = c(123, 42, 23, 5, 42, 4, 23, 25, 42, 23, NA, 5563,56), 
            Year = c(1990, 1991, 1992, 1993, 1991, 1995, 1996, 1997, 1991, 1992, 2000, 2001,2002))

最终数据集应如下所示

 df2 = data.frame(code = c("AFG", "AGO", "ALB", "AND", "ARB", "ARE", "ARG", "ARM", "ASM", "ATG", "AUS", "AUT","AUT"),
             val= c(123, 42, 23, 5, 42, 4, 23, 25, 42, 23, NA, 5563,56),
             Year = c(1990, 1991, 1992, 1993, 1991, 1995, 1996, 1997, 1991, 1992, 2000, 2001,2002), newval=c(NA,NA,NA,NA,NA,0.032520325,0.547619048,1.086956522,NA,NA,NA,241.8695652,2.24))

Answer 1

在基数R中，我们可以使用 match

df2$new_val <- with(df2, val/val[match(Year - 5, Year)])

df2
#   code  val Year  new_val
#1   AFG  123 1990       NA
#2   AGO   42 1991       NA
#3   ALB   23 1992       NA
#4   AND    5 1993       NA
#5   ARB   42 1991       NA
#6   ARE    4 1995   0.0325
#7   ARG   23 1996   0.5476
#8   ARM   25 1997   1.0870
#9   ASM   42 1991       NA
#10  ATG   23 1992       NA
#11  AUS   NA 2000       NA
#12  AUT 5563 2001 241.8696
#13  AUT   56 2002   2.2400