阅读CSV文件时如何跳过列？

Question

根据文件read.csv,colClasses论证:

可能的值是......,"NULL"(跳过列时),...

但看起来它在col.names使用时不起作用:

columnHeaders <- c("column1", "column2", "column_to_skip")
columnClasses <- c("factor", "factor", NULL)
data <- read.csv(fileCSV, header = FALSE, sep = ",", col.names = columnHeaders, colClasses = columnClasses)

结果data包含3列,包括column_to_skip.没有这个最后一列,读取csv的正确方法是什么？

Answer 1

用"NULL"而不是NULL:

csv <- "1,2,3
4,5,6"
read.csv(text = csv, header = FALSE, colClasses = c("integer", "integer", "NULL"))
#   V1 V2
# 1  1  2
# 2  4  5