R语言读取大数据 data.table包 fread函数

> 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)