如何在循环中调用函数以计算 R 中的加权交叉表

Question

我想计算变量x和同一dataframe的几个y变量之间的多个加权交叉表。我创建了一个函数来做到这一点，但我无法循环我的y变量列表。

我举了一个使用mpg数据的过程示例：在这里，我的y变量是cyl和year。xclass.

library(questionr)
# include some weights in mpg2 (same weight)
mpg2 <- mpg %>%
mutate(weight = 1/234)
#> Error in mpg %>% mutate(weight = 1/234): could not find function "%>%"
# crosstab class by cyl using weights
questionr::wtd.table(mpg2$class, mpg2$cyl,
weights=mpg2$weight,
digits = 0, na.show=FALSE)
#> Error in questionr::wtd.table(mpg2$class, mpg2$cyl, weights = mpg2$weight, : object 'mpg2' not found
# using a function
calc_table <- function(x, y) {
return(questionr::wtd.table(x, y,
weights=mpg2$weight,
digits = 0, na.show=FALSE))
}
# No problem when describing the variable as mpg2$cyl
calc_table(mpg2$class, mpg2$cyl)
#> Error in questionr::wtd.table(x, y, weights = mpg2$weight, digits = 0, : object 'mpg2' not found
# But I want to crosstab class with cyl (mpg2[5])
# and also class with year (mpg2[4]) 
# referencing the variable in a loop
# My main goal is to use the function for several variables
for (i in c(4:5)){
calc_table(mpg2$class, mpg2[i])
}
#> Error in questionr::wtd.table(x, y, weights = mpg2$weight, digits = 0, : object 'mpg2' not found

Answer 1

问题是您使用了返回数据帧或 tibble 的mpg2[i]，而不是返回向量的mpg2[[i]]。但是，除了这个问题之外，我建议循环使用列名而不是位置。我还添加了一个列表来保存结果。试试这个：

library(dplyr)
library(questionr)
# include some weights in mpg2 (same weight)
mpg2 <- ggplot2::mpg %>%
mutate(weight = 1/234)
# using a function
calc_table <- function(x, y) {
questionr::wtd.table(x, y, weights=mpg2$weight, digits = 0, na.show=FALSE)
}
table_list <- list()
for (i in c("cyl", "year")){
print(table_list[[i]] <- calc_table(mpg2$class, mpg2[[i]]))
}
#>                      4           5           6           8
#> 2seater    0.000000000 0.000000000 0.000000000 0.021367521
#> compact    0.136752137 0.008547009 0.055555556 0.000000000
#> midsize    0.068376068 0.000000000 0.098290598 0.008547009
#> minivan    0.004273504 0.000000000 0.042735043 0.000000000
#> pickup     0.012820513 0.000000000 0.042735043 0.085470085
#> subcompact 0.089743590 0.008547009 0.029914530 0.021367521
#> suv        0.034188034 0.000000000 0.068376068 0.162393162
#>                   1999        2008
#> 2seater    0.008547009 0.012820513
#> compact    0.106837607 0.094017094
#> midsize    0.085470085 0.089743590
#> minivan    0.025641026 0.021367521
#> pickup     0.068376068 0.072649573
#> subcompact 0.081196581 0.068376068
#> suv        0.123931624 0.141025641