R语言中 attach()与detach()，及with()的使用
attach(what, pos = 2L, name = deparse(substitute(what), backtick=FALSE),
warn.conflicts = TRUE)1.attach()是对what添加路径索引，避免重复输入what名称，参数解释如下：
- what：数据框或列表；
- pos=2L：添加的路径存储的位置，一般默认即可。在对多个数据添加索引时，此位置会变成3L,4L,5L...detach()撤销索引路径时，会撤销对应位置的索引储存，具体例子见后；
- name：不懂，遇见需要的情况再补充；
- backtick=FALSE：反引号，经过测试，该参数固定为FALSE不可调，再调用索引时会用到；
- warn.conflicts：是否打印警告。
detach()是撤销attach()建立的路径索引，往往二者配套使用。
举例如下：
> class(data) #data为自己提供的数据
[1] "data.frame"
> colnames(data) #查看data列
[1] "No." "Component Name" "Mass Info" "Retention Time"
[5] "QCRSD" "P-value" "Fold change" "A-1"
[9] "A-2" "A-3" "B-1" "B-2"
[13] "B-3" "QC1" "QC2" "QC3"
[17] "as.is"
> attach(data)
The following objects are masked from data (pos = 3):
A-1, A-2, A-3, as.is, B-1, B-2, B-3, Component Name, Fold change,
Mass Info, No., P-value, QC1, QC2, QC3, QCRSD, Retention Time
The following objects are masked from data (pos = 4):
A-1, A-2, A-3, as.is, B-1, B-2, B-3, Component Name, Fold change,
Mass Info, No., P-value, QC1, QC2, QC3, QCRSD, Retention Time
>No.
[1] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
[26] 26
> A-1
Error: object 'A' not found #因为列名“A-1”不符合变量命名规则，此处可用check.names=T改变，会
#改为A.1
> `A-1` #用反引号辅助读取A-1列信息
[1] 6.112652e+07 5.338550e+06 9.803146e+07 1.698537e+07 3.193722e+07 2.111517e+07
[7] 7.825601e+06 2.726090e+07 1.062785e+07 1.018187e+08 1.051693e+07 1.336919e+07
[13] 5.948830e+04 2.090497e+06 5.882181e+06 4.733337e+07 5.974494e+05 2.444981e+07
[19] 8.283025e+03 2.215970e+04 7.372889e+05 5.948745e+05 2.102290e+07 9.133244e+06
[25] 3.996773e+07 4.434691e+05
> data$`A-1` #与上述建立路径索引结果相同
[1] 6.112652e+07 5.338550e+06 9.803146e+07 1.698537e+07 3.193722e+07 2.111517e+07
[7] 7.825601e+06 2.726090e+07 1.062785e+07 1.018187e+08 1.051693e+07 1.336919e+07
[13] 5.948830e+04 2.090497e+06 5.882181e+06 4.733337e+07 5.974494e+05 2.444981e+07
[19] 8.283025e+03 2.215970e+04 7.372889e+05 5.948745e+05 2.102290e+07 9.133244e+06
[25] 3.996773e+07 4.434691e+05
> summary(QC1,`A-1`)
Min. 1st Qu. Median Mean 3rd Qu. Max.
4149 1194476 12129322 21224523 30429375 104915075
> summary(data$QC1,data$`A-1`)
Min. 1st Qu. Median Mean 3rd Qu. Max.
4149 1194476 12129322 21224523 30429375 104915075
> summary(`A-1`,`Fold change`)
Min. 1st Qu. Median Mean 3rd Qu. Max.
8283 1075591 10572393 21472932 26558125 101818722
> summary(data$`Fold change`,data$`A-1`)
Min. 1st Qu. Median Mean 3rd Qu. Max.
0.633 1.256 1.444 1.433 1.590 2.649
> detach(data)
> No. #如果发现还能出结果...那就多detach几次==
Error: object 'No.' not found2.with()函数
with(data, expr, ...) #data可以是an environment, a list, a data frame, or an integer as in
#sys.call
within(data, expr, ...) #data为列表或数据框
within(data, expr, keepAttrs = TRUE, ...)- within()函数中data必须是列表或数据框，with()中data类型更广
- 表达式，大括号{}之间的语句都只针对data执行，但如果大括号中只有一句的话，则省略大括号。
> with(data,{No.}) #No.符合变量命名标准，可直接查看
[1] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
[17] 17 18 19 20 21 22 23 24 25 26
> with(data,{A-1}) #A-1不符合变量命名标准，不可直接查看，需要用反引号调用
Error in eval(substitute(expr), data, enclos = parent.frame()) :
object 'A' not found
> with(data,{`A-1`})
[1] 6.112652e+07 5.338550e+06 9.803146e+07
[4] 1.698537e+07 3.193722e+07 2.111517e+07
[7] 7.825601e+06 2.726090e+07 1.062785e+07
[10] 1.018187e+08 1.051693e+07 1.336919e+07
[13] 5.948830e+04 2.090497e+06 5.882181e+06
[16] 4.733337e+07 5.974494e+05 2.444981e+07
[19] 8.283025e+03 2.215970e+04 7.372889e+05
[22] 5.948745e+05 2.102290e+07 9.133244e+06
[25] 3.996773e+07 4.434691e+05
> `A-1` #with函数中路径索引不能在外部调用，需要用<<- 赋值才可以
Error: object 'A-1' not found
> with(data,{a-1<<-`A-1`}) #a-1符合变量命名标准，需要用反引号建立变量名
Error in a - 1 <<- `A-1` : object 'a' not found
> with(data,{a<<-`A-1`})
> a
[1] 6.112652e+07 5.338550e+06 9.803146e+07
[4] 1.698537e+07 3.193722e+07 2.111517e+07
[7] 7.825601e+06 2.726090e+07 1.062785e+07
[10] 1.018187e+08 1.051693e+07 1.336919e+07
[13] 5.948830e+04 2.090497e+06 5.882181e+06
[16] 4.733337e+07 5.974494e+05 2.444981e+07
[19] 8.283025e+03 2.215970e+04 7.372889e+05
[22] 5.948745e+05 2.102290e+07 9.133244e+06
[25] 3.996773e+07 4.434691e+05
> with(data,{`a-1` <<- `A-1`})
> a-1
[1] 6.112652e+07 5.338549e+06 9.803146e+07
[4] 1.698537e+07 3.193722e+07 2.111517e+07
[7] 7.825600e+06 2.726090e+07 1.062785e+07
[10] 1.018187e+08 1.051693e+07 1.336919e+07
[13] 5.948730e+04 2.090496e+06 5.882180e+06
[16] 4.733337e+07 5.974484e+05 2.444981e+07
[19] 8.282025e+03 2.215870e+04 7.372879e+05
[22] 5.948735e+05 2.102290e+07 9.133243e+06
[25] 3.996773e+07 4.434681e+05
> with(data,{plot(No.,`A-1`)}) #{}中可以进行复杂计算