计算R中的平均指数与指数之比

Question

我有一个统计问题，我想用R解决。假设我有2个索引，Index1描述了一段时间内的平均价格水平，Index2描述了一段时间内的平均租金水平。

这是我的数据（框架）：

Year    Index1  Index2
1995    100     77.0033
1996    106.63  79.3342
1997    110.45  81.8608
1998    114.4   84.0633
1999    121.75  86.1133
2000    130.59  88.7758
2001    148.85  91.4483
2002    161.43  93.9042
2003    179.39  95.57
2004    204.59  97.1075
2005    227.58  99.9995
2006    253.17  102.2792
2007    277.45  104.0525
2008    276.42  107.1633
2009    261.26  109.8667
2010    280.81  111.9058
2011    295.91  114.0408
2012    306.63  115.56
2013    NA      117.2691
2014    NA      118.2967

编辑：我想计算价格与租金的平均值，换句话说，就是Index1 / Index2的长期平均比率。之后我想计算平均值的百分比差异（每年）。我怎么能这样做？

祝你好运， 吉尔斯

编辑：这是dput（df）

structure(list(Year = c(1995, 1996, 1997, 1998, 1999, 2000, 2001, 
2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 
2013, 2014), Price = c("100", "106.63", "110.45", "114.4", "121.75", 
"130.59", "148.85", "161.43", "179.39", "204.59", "227.58", "253.17", 
"277.45", "276.42", "261.26", "280.81", "295.91", "306.63", "NA", 
"NA"), Rent = c(77.0033, 79.3342, 81.8608, 84.0633, 86.1133, 
88.7758, 91.4483, 93.9042, 95.57, 97.1075, 99.9995, 102.2792, 
104.0525, 107.1633, 109.8667, 111.9058, 114.0408, 115.56, 117.2691, 
118.2967)), .Names = c("Year", "Price", "Rent"), row.names = c(NA, 
-20L), class = "data.frame")

Answer 1

如果我明白你的意思，首先要平均Index1/Index2，即（假设您的数据框为df）：

average = mean(df$Index1/df$Index2, na.rm = TRUE)

然后在数据框中添加一列以显示年度变化（例如增加为正数）：

df$variation = df$Index1/df$Index2/average - 1

Answer 2

根据您在评论中发布的所需输出，我可以建议此代码：

library(ggplot2)
df              <- data.frame(apply(df, 2, as.numeric))
df['Rent_b100'] <- df$Rent/df$Rent[1]*100
df['ratio']     <- with(df, Price/Rent_b100)
average_ratio   <- mean(df$ratio, na.rm=T)

ggplot(data=df) + 
  geom_line(aes(x=Year, y=ratio), color="blue", size=2) +
  geom_hline(yintercept=average_ratio, color="purple",size=2) +
  geom_text(data=data.frame(y=c(2, 1.2), x=mean(df$Year), label=c("rent", "buy")), 
            aes(x=x, y=y, label=label), size=8) +
  geom_text(aes(x=df$Year[1], y=average_ratio*1.05, label=round(average_ratio, 2)), color="purple")

其中给出了以下图表：