r - 如何使用 R 中的 if 语句将唯一函数应用于数据集的多行？

Question

在这个数据集 (df) 中，我想根据物种应用不同的方程来计算存储在“Std.Val1”中的新输出

Year Site Quadrant species Val1 Val2 Std.Val1
2019   1     1        A    20    30     NA
2019   1     1        B    NA    25     NA
2019   1     2        C    20    10     NA
2019   1     2        D    11    22     NA

c_A <- 1
m_A <- 2

c_B <- 2
m_B <- 5

c_C <- 10
m_C <- 12

c_D <- 11
m_D <- 2

我尝试关注 this example写我的代码

df %>%
    mutate(
      Std.Val1 = ifelse(species == "A" ~ ((log(Val1) - c_A )/(m_A)),
                 ifelse(species == "B" ~ ((log(Val1) - c_B )/(m_B)),
                 ifelse(species == "C" ~ ((log(Val1) - c_C )/(m_C)),
                 ifelse(species == "D" ~ ((log(Val1) - c_D )/(m_D)), NA))))
              )

但我一直遇到如下错误:“错误:mutate() 输入 Std.Val1 出现问题。x“语言”对象不能被强制输入“逻辑”ℹ 输入 nem1 为 ifelse(...)"

Answer 1

这是一种避免大量输入的 data.table 方法

library(data.table)
# Sample data
DT <- fread("Year Site Quadrant species Val1 Val2
2019   1     1        A    20    30     
2019   1     1        B    NA    25     
2019   1     2        C    20    10     
2019   1     2        D    11    22     ")
# Create lookup table with values to calculate with
DT.lookup <- data.table( species = LETTERS[1:4], 
                         vc = c(1,2,10,11), 
                         vm = c(2,3,12,2))
#    species vc vm
# 1:       A  1  2
# 2:       B  2  3
# 3:       C 10 12
# 4:       D 11  2

# Join and calculate in 1 step
DT[DT.lookup, Std.Val1 := (log(Val1) - i.vc )/(i.vm), on = .(species)][]

#    Year Site Quadrant species Val1 Val2   Std.Val1
# 1: 2019    1        1       A   20   30  0.9978661
# 2: 2019    1        1       B   NA   25         NA
# 3: 2019    1        2       C   20   10 -0.5836890
# 4: 2019    1        2       D   11   22 -4.3010524