如何使用R查找多列中的比率差异

Question

我的数据框包含 4 个不同年份的值。我需要找出这些值在所有年份中是如何变化的，即哪个城市的值变化太频繁，哪个最少。

City     Ratio1     Ratio2     Ratio3     Ratio4
A        1.0177722  1.0173251  1.0133026  1.0140027
B        1.0132619  1.0122653  1.0128473  1.0111068
C        1.0689484  1.0640355  1.0625305  1.0544790

..... other 1000 entries

我试过通过差异来做到这一点，但没有运气。问题是哪个城市的比例在 ratio1 到 ratio4 之间变化最大，哪个城市变化最小。我尝试使用 mutate 函数来计算方差，但它向我发出警告：

DF<- DF%>% mutate(vari = var(Ratio1:Ratio4,na.rm = T))

Warning messages:
1: In POP_2013_ratio:POP_2016_ratio :
  numerical expression has 439 elements: only the first used
2: In POP_2013_ratio:POP_2016_ratio :
  numerical expression has 439 elements: only the first used

Answer 1

R 的 data.table 包有一种非常简洁的方法可以根据现有列创建新列：

dt <- data.table(City = c("A", "B", "C"),
                 Ratio1 = c(1.0177722, 1.0132619, 1.0689484),
                 Ratio2 = c(1.0173251, 1.0122653, 1.0640355), 
                 Ratio3 = c(1.0133026, 1.0128473, 1.0625305), 
                 Ratio4 = c(1.0140027,1.0111068, 1.0544790))
>dt 
   City   Ratio1   Ratio2   Ratio3   Ratio4
1:    A 1.017772 1.017325 1.013303 1.014003
2:    B 1.013262 1.012265 1.012847 1.011107
3:    C 1.068948 1.064035 1.062531 1.054479

您可以试用一些功能，然后看看最适合您的功能：

 dt[, diff := Ratio4-Ratio1
    ][, abs_diff := abs(Ratio4-Ratio1)
      ][, range:= max(c(Ratio1, Ratio2, Ratio3, Ratio4))-  min(c(Ratio1, Ratio2, Ratio3, Ratio4)), by = City
        ][,variance:=var(c(Ratio1, Ratio2, Ratio3, Ratio4)), by = City]

 >dt

    City   Ratio1   Ratio2   Ratio3   Ratio4       diff  abs_diff     range     variance
 1:    A 1.017772 1.017325 1.013303 1.014003 -0.0037695 0.0037695 0.0044696 5.174612e-06
 2:    B 1.013262 1.012265 1.012847 1.011107 -0.0021551 0.0021551 0.0021551 8.766456e-07
 3:    C 1.068948 1.064035 1.062531 1.054479 -0.0144694 0.0144694 0.0144694 3.609233e-05

当您最终决定要使用的标准（比方说，方差）时，您可以 select 顶级城市使用：

dt[order(-variance)][1]

>dt
   City   Ratio1   Ratio2   Ratio3   Ratio4       diff  abs_diff     range     variance
1:    C 1.068948 1.064035 1.062531 1.054479 -0.0144694 0.0144694 0.0144694 3.609233e-05

如何使用R查找多列中的比率差异

How to find the difference of ratio in multiple columns using R

diff

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