我创建的函数抛出未知或单位化的列错误

Question

我正在尝试创建如下功能：

LogVolLR <- function(x, y, z) {

  for (i in 2:nrow(x)) {

    x$y[i] <- (1 - 0.5) * x$y[i-1] + 3 + 8 * x$z[i]

  }
}

但是，当我在数据帧上应用此函数时，出现未知或统一的列错误。请在下面找到一个示例：

library(tidyverse)
set.seed(50)

df <- data_frame(SlNo = 1:2000,
                 Scenario = rep(c(1, 2, 3, 4),500),
                 A = round(rnorm(2000, 11, 6)),
                 B = round(rnorm(2000, 15, 4))) %>%
  arrange(Scenario) 

df<- df %>% split(f = .$Scenario) %>%
  map_dfr(~bind_rows(tibble(Scenario = 0), .x)) 

df <- df %>% mutate(C = if_else(Scenario != 0, 0, 4),
                    E = if_else(Scenario != 0, 0, 6))

LogVolLR(df, y = C, z = B)


> LogVolLR(df, y = C, z = B)

There were 50 or more warnings (use warnings() to see the first 50)

Warning messages:
1: Unknown or uninitialised column: 'y'.
2: Unknown or uninitialised column: 'y'.
3: Unknown or uninitialised column: 'z'.

我不确定我是否正确编写了函数。任何帮助将不胜感激