学习笔记，仅供参考，有错必纠，按需更新
PS：大量参考R的帮助文档，照搬英文不翻译
subset函数
所在包：base
描述
Return subsets of vectors, matrices or data frames which meet conditions.
使用
subset(x, ...)
## Default S3 method:
subset(x, subset, ...)
## S3 method for class 'matrix'
subset(x, subset, select, drop = FALSE, ...)
## S3 method for class 'data.frame'
subset(x, subset, select, drop = FALSE, ...)
参数
参数 | 解释 |
x | object to be subsetted |
subset | logical expression indicating elements or rows to keep: missing values are taken as false. |
select | expression, indicating columns to select from a data frame |
drop | passed on to [ indexing operator. |
举个例子
我们利用鸢尾花数据集iris来做这个实验，首先选择Species等于 “setosa” 且 Petal.Length 小于1.5的样本，只返回Sepal.Length, Petal.Length, Species列：
data("iris")
testdf <- subset(iris, Species == "setosa" & Petal.Length < 1.5,
select = c(Sepal.Length, Petal.Length, Species))
testdf输出：
Sepal.Length Petal.Length Species
1 5.1 1.4 setosa
2 4.9 1.4 setosa
3 4.7 1.3 setosa
5 5.0 1.4 setosa
7 4.6 1.4 setosa
9 4.4 1.4 setosa
13 4.8 1.4 setosa
14 4.3 1.1 setosa
15 5.8 1.2 setosa
17 5.4 1.3 setosa
18 5.1 1.4 setosa
23 4.6 1.0 setosa
29 5.2 1.4 setosa
34 5.5 1.4 setosa
36 5.0 1.2 setosa
37 5.5 1.3 setosa
38 4.9 1.4 setosa
39 4.4 1.3 setosa
41 5.0 1.3 setosa
42 4.5 1.3 setosa
43 4.4 1.3 setosa
46 4.8 1.4 setosa
48 4.6 1.4 setosa
50 5.0 1.4 setosa
