> setwd("D:\\R_Tardy")
> library(data.table)
// data.table 1.9.6
// For help type ?data.table or
// https://github.com/Rdatatable/data.table/wikiThe fastest way to learn (by data.table authors):
// https://www.datacamp.com/courses/data-analysis-the-data-table-way
> TestDT <- fread("test.txt", sep = "\t",header = FALSE, na.strings = "NA")
// 查看文件前几行
> head(TestDT)
// 重 命 名 列的名字
> colnames(TestDT) <- c("ID","num","desc")
> head(TestDT)
> df <- TestDT[TestDT$desc %in% c("Heat group"), 1:ncol(TestDT), with=FALSE]
> df1 <- data.frame(df)
> nrow(df1)原文：http://matrix6ro.blog.51cto.com/1746429/1790941