1. rev VS reverse
data = c("abc", "dba", "ywc", "tdq", "arc")
rev(data)
[1] "arc" "tdq" "ywc" "dba" "abc"
reverse(data)
[1] "cba" "abd" "cwy" "qdt" "cra"
base::rev(): rev provides a reversed version of its argument. [1]
IRanges::reverse(): A generic function for reversing vector-like or list-like objects. This man page describes methods for reversing a character vector, a Views object, or a MaskCollection object.[2]
总结：
rev与reverse函数都是将目前的排列次序进行反向排列，不同点是：rev针对的是整个向量，而reverse针对的是向量中的每一个字符串
2.order 可对数据框按列进行重新排序（按行排序同理）
data = c("abc", "dba", "ywc", "tdq", "arc")
order(data)
[1] 1 5 2 4 3
data[order(data)]
[1] "abc" "arc" "dba" "tdq" "ywc"
data[order(data, decreasing = TRUE)]
[1] "ywc" "tdq" "dba" "arc" "abc"
base::order(): order returns a permutation which rearranges its first argument into ascending or descending order, breaking ties by further arguments.[3]
总结：order是按照其元素值的大小对向量进行重新排序，并返回其索引。
巧用order，对数据框进行排序
dt = data.frame(a=c(3,5,1,2,2), b=c(7,2,1,4,3), c=c("m2", "y1", "o3", "p2","p3"))
dt
a b c
1 3 7 m2
2 5 2 y1
3 1 1 o3
4 2 4 p2
5 2 3 p3
dt[order(dt$a), ] #根据第一列升序对数据框进行重新排序
a b c
3 1 1 o3
4 2 4 p2
5 2 3 p3
1 3 7 m2
2 5 2 y1
dt[order(dt$a, dt$b), ] #先根据第一列升序排序，若第一列值相等，则比较第二列值，按照其升序进行排序
a b c
3 1 1 o3
5 2 3 p3
4 2 4 p2
1 3 7 m2
2 5 2 y1
3.arrange（来源于dplyr包，这个包很实用，后续会做更多的介绍）
dt
a b c
1 3 7 m2
2 5 2 y1
3 1 1 o3
4 2 4 p2
5 2 3 p3
arrange(dt,a,b) #与order的结果一样，用法更简便
a b c
1 1 1 o3
2 2 3 p3
3 2 4 p2
4 3 7 m2
5 5 2 y1
dplyr::arrange()：arrange orders the rows of a data frame by the values of selected columns.[4]
总结：arrange更适用于对数据框按照列排序，且用法很简单
4.sort
data
[1] "abc" "dba" "ywc" "tdq" "arc"
sort(data)
[1] "abc" "arc" "dba" "tdq" "ywc"
sort(data, decreasing = T)
[1] "ywc" "tdq" "dba" "arc" "abc"
base::sort():Sort (or order) a vector or factor (partially) into ascending or descending order.[5]
总结：sort是按照其元素值的大小对向量进行重新排序，并返回重排之后的值
5.rank 一般用于排名
s = c(3,2,4,1,3,4,5,7,8)
rank(s)
[1] 3.5 2.0 5.5 1.0 3.5 5.5 7.0 8.0 9.0
base::rank(): Returns the sample ranks of the values in a vector.[6]
总结：rank返回原数据的秩序。
References
[1]Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
[2]Lawrence M, Huber W, Pagès H, Aboyoun P, Carlson M, Gentleman R, Morgan M, Carey V (2013). “Software for Computing and Annotating Genomic Ranges.” PLoS Computational Biology, 9.
[3]Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
[4]Wickham, H., François, R., Henry, L., & Müller, K. (2020). A Grammar of Data Manipulation [R package dplyr version 1.0.2].
[5]Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988). The New S Language. Wadsworth & Brooks/Cole.
[6]Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole
