R语言里面的data.frame就是数据库里面的table，R语言的分析，建模大部分都是基于data.frame数据结构，由rows和columns组成。data.frame每一个column会存储同样的数据类型，可以是numeric, factor, character.
创建一个data.frame
R用data.frame() function创建一个data.frame
data.frame(..., row.names = NULL, check.rows = FALSE,check.names = TRUE, fix.empty.names = TRUE,stringsAsFactors = default.stringsAsFactors())# create data.framestudentAges <- c(23, 34, 34, 89, 90, 340)studentNames <- c("Bob","Henry","Lily","LiMing","Rose","Jack")studentDF <- data.frame(studentAges, studentNames)studentDFrownames(studentDF)colnames(studentDF)
rownames和colnames可以用来看行名和列名。
data.frame 增加一列
# add a column to data.framestudentHeight <- c(150, 165, 180, 155, 167, 186)studentDF <- cbind(studentDF, studentHeight)studentDF
data.frame 增加一行
# add a row to data.framenewStudent <- list(34, "Winters", "190")studentDF <- rbind(studentDF, newStudent)studentDF
查看data.frame的结构，str
# check data.frame structure with strstr(studentDF)
5. 获取data.frame部分数据,subset
# this will get the row 1 and column 2 elementstudentDF[1,2]# this will get the whole firt rowstudentDF[1,]# this will get the whole second columnstudentDF[,2]# you also can get several rows or columns togetherstudentDF[2:4,]
data.frame里面查找符合条件的rows
# find a row in data.frame, in this, to find height>170# studentDF[,3] > 170 this will give a true, false vectorvalidStudentDF <- studentDF[studentDF[,3] > 170,]
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