R语言读取制表符分隔txt文件时遇报错问题求助

Hey there! Let's work through your file import issues step by step and get you only the last two columns you need.

First: Fixing the "Line X did not have 4 elements" Error (Absolute Path) #

That error is confusing since you said your file only has 100 lines—here's what's likely going on:

• Your file might have hidden empty lines, extra newline characters, or some lines where tab separators are missing (like spaces used instead of tabs in spots). R counts these as additional "lines" even if they look blank.
• Try these quick fixes:
  1. Use fill=TRUE to let R automatically fill missing elements with NA instead of throwing an error:

     movieTimes <- read.table("your_absolute_path_here", header=F, sep='\t', fill=TRUE)
     

  2. Skip empty lines with skipNul=TRUE:

     movieTimes <- read.table("your_absolute_path_here", header=F, sep='\t', skipNul=TRUE)
     

  3. Inspect your file content first to spot weird lines:

     # Check the first 10 lines
     head(readLines("your_absolute_path_here"), 10)
     # See how many lines R actually detects
     length(readLines("your_absolute_path_here"))
     

  4. Use data.table::fread (it's way more robust for messy text files):

     library(data.table)
     movieTimes <- fread("your_absolute_path_here", header=F, sep='\t')
     

Second: Fixing the Relative Path Error #

This error means R can't find movies.txt in your current working directory. Here's how to fix it:

• Check your current working directory:

  getwd()
  

• Move movies.txt to that folder, or set your working directory to where the file lives:

  setwd("path/to/the/folder/with/movies.txt")
  

• Or use file.choose() to manually select the file (no more path guesswork!):

  movieTimes <- read.table(file.choose(), header=F, sep='\t')
  

Finally: Only Import the Last Two Columns #

Once you can import the full file, you can grab just the last two columns. Even better—you can skip importing the first two columns entirely to save time:

Method 1: Import all columns, then subset #

# After importing the full table
movieTimes_last_two <- movieTimes[, c(3,4)]

Method 2: Skip first two columns during import (more efficient) #

Use colClasses to tell R to ignore the first two columns:

movieTimes_last_two <- read.table("your_path_here", header=F, sep='\t', colClasses=c("NULL", "NULL", "character", "numeric"))
# Adjust "character" and "numeric" to match your actual column data types

Method 3: Use fread to select only the last two columns #

If you're using data.table, this is super clean:

library(data.table)
movieTimes_last_two <- fread("your_path_here", header=F, sep='\t', select=c(3,4))

内容的提问来源于stack exchange，提问作者Stacey K.