如何在R中拆分列? [英] How to split a column in R?

问题描述

有人知道如何将一列拆分为多列吗?例如:我想拆分score"和class"列，然后将grade"列的值作为列名.在我的数据中，我在等级"列中有 50 个不同的值，而不是在下面的示例中只有两个.在数据框 2 中，行名称是数据框 1 中列class"的值.

Anyone know how can I split a column to multiple ones? For example: I want to split column "score" and "class", then make the values of column "grade" as column name. In my data, I have 50 different values in column "grade" instead of only two in the example below. In the data frame 2, the row names are the values of column "class" in data frame 1.

数据框 1

class   grade   score
A          a    12
B          a    45
C          a    75
D          a    18
E          a    6
A          b    45
B          b    92
C          b    78
D          b    36
E          b    39

数据框 2

    a   b
A   12  45
B   45  92
C   75  78
D   18  36
E   6   39

推荐答案

Base R 的 unstack 开箱即用:

Base R's unstack does this out of the box:

unstack(df, score ~ grade)
#   a  b
#1 12 45
#2 45 92
#3 75 78
#4 18 36
#5  6 39

和 xtabs 一样:

as.data.frame.matrix(xtabs(score ~ class + grade, data=df))

#   a  b
#A 12 45
#B 45 92
#C 75 78
#D 18 36
#E  6 39

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