R 按组提取变量最小值对应的行
我希望(1)按一个变量(R 按组提取变量最小值对应的行,r,dplyr,data.table,aggregate,R,Dplyr,Data.table,Aggregate,我希望(1)按一个变量(State)对数据进行分组,(2)在每个组中查找另一个变量的最小值行(Employees),以及(3)提取整行 (1) 和(2)是简单的一行,我觉得(3)也应该是,但我不能得到它 以下是一个示例数据集: > data State Company Employees 1 AK A 82 2 AK B 104 3 AK C 37 4 AK D
State
)对数据进行分组,(2)在每个组中查找另一个变量的最小值行(Employees
),以及(3)提取整行
(1) 和(2)是简单的一行,我觉得(3)也应该是,但我不能得到它
以下是一个示例数据集:
> data
State Company Employees
1 AK A 82
2 AK B 104
3 AK C 37
4 AK D 24
5 RI E 19
6 RI F 118
7 RI G 88
8 RI H 42
data <- structure(list(State = structure(c(1L, 1L, 1L, 1L, 2L, 2L, 2L,
2L), .Label = c("AK", "RI"), class = "factor"), Company = structure(1:8, .Label = c("A",
"B", "C", "D", "E", "F", "G", "H"), class = "factor"), Employees = c(82L,
104L, 37L, 24L, 19L, 118L, 88L, 42L)), .Names = c("State", "Company",
"Employees"), class = "data.frame", row.names = c(NA, -8L))
…或数据。表:
> library(data.table)
> DT <- data.table(data)
> DT[ , list(Employees = min(Employees)), by = State]
State Employees
1: AK 24
2: RI 19
>库(data.table)
>DT[,列表(员工=min(员工)),按=州]
国家雇员
1:AK 24
2:RI 19
但是如何提取与这些min
值对应的整行,即在结果中也包括公司
稍微优雅一点:
library(data.table)
DT[ , .SD[which.min(Employees)], by = State]
State Company Employees
1: AK D 24
2: RI E 19
与使用.SD
相比,稍微不那么优雅,但速度要快一点(对于包含多个组的数据):
另外,如果您的数据集有多个相同的最小值,并且您希望将它们全部子集,则只需将表达式which.min(Employees)
替换为Employees==min(Employees)
另请参见。稍微优雅一点:
library(data.table)
DT[ , .SD[which.min(Employees)], by = State]
State Company Employees
1: AK D 24
2: RI E 19
与使用.SD
相比,稍微不那么优雅,但速度要快一点(对于包含多个组的数据):
另外,如果您的数据集有多个相同的最小值,并且您希望将它们全部子集,则只需将表达式which.min(Employees)
替换为Employees==min(Employees)
另请参见。基本函数通常用于处理data.frames中的块数据。比如说
by(data, data$State, function(x) x[which.min(x$Employees), ] )
它确实返回列表中的数据,但您可以使用
do.call(rbind, by(data, data$State, function(x) x[which.min(x$Employees), ] ))
基本函数by
通常用于处理data.frames中的块数据。比如说
by(data, data$State, function(x) x[which.min(x$Employees), ] )
它确实返回列表中的数据,但您可以使用
do.call(rbind, by(data, data$State, function(x) x[which.min(x$Employees), ] ))
这里有一个dplyr
解决方案(请注意,我不是一个普通用户):
这里有一个dplyr
解决方案(请注意,我不是一个普通用户):
由于这是谷歌的热门产品,我想我会添加一些我觉得有用的额外选项。这个想法基本上是由员工安排一次,然后根据状态
使用data.table
library(data.table)
unique(setDT(data)[order(Employees)], by = "State")
# State Company Employees
# 1: RI E 19
# 2: AK D 24
或者,我们也可以先下订单,然后再下子集.SD
。这两种操作在最近的数据中都得到了优化。表版本和顺序似乎触发了数据。表:::forerv
,而.SD[1L]
触发了Gforce
setDT(data)[order(Employees), .SD[1L], by = State, verbose = TRUE] # <- Added verbose
# order optimisation is on, i changed from 'order(...)' to 'forder(DT, ...)'.
# i clause present and columns used in by detected, only these subset: State
# Finding groups using forderv ... 0 sec
# Finding group sizes from the positions (can be avoided to save RAM) ... 0 sec
# Getting back original order ... 0 sec
# lapply optimization changed j from '.SD[1L]' to 'list(Company[1L], Employees[1L])'
# GForce optimized j to 'list(`g[`(Company, 1L), `g[`(Employees, 1L))'
# Making each group and running j (GForce TRUE) ... 0 secs
# State Company Employees
# 1: RI E 19
# 2: AK D 24
从awesome answer中借用的另一个有趣的想法(以mult=“first”
的形式进行了一个小的修改,以处理多个匹配)是首先找到每个组的最小值,然后执行二进制连接。这样做的优点是利用了data.tablesgmin
函数(它跳过了计算开销)和二进制连接特性
tmp%切片(1),
“(plyr)ddply/which.min:”=ddply(数据、(状态)、函数(x)x[which.min(x$Employees),),
“(base)by:”=do.call(rbind,by(data,data$State,function(x)x[which.min(x$Employees),]))
#单位:毫秒
#expr最小lq平均uq最大neval cld
#(数据表).SD[哪个最小值]:119.66086 125.49202 145.57369 129.61172 152.02872 267.5713 100 d
#(数据表).I[哪个最小值]:12.84948 13.66673 19.51432 13.97584 15.17900 109.5438 100 a
#(数据表)顺序/唯一性:52.91915 54.63989 64.39212 59.15254 61.71133 177.1248 100 b
#(data.table)order/.SD[1L]:51.41872 53.22794 58.17123 55.00228 59.00966 145.0341 100 b
#(data.table)自联接(on):44.37256 45.67364 50.32378 46.24578 50.69411 137.4724 100 b
#(data.table)自连接(设置键):14.3054315.2892418.6373915.5866716.01017106.0069100A
#(dplyr)切片(which.min):82.60453 83.64146 94.06307 84.82078 90.09772 186.0848 100 c
#(dplyr)排列/区分:344.81603360.09167385.52661379.55676395.29463491.3893 100 e
#(dplyr)排列/分组单位/切片:367.95924 383.52719 414.99081 397.93646 425.92478 557.9553 100 f
#(plyr)ddply/which.min:506.55354 530.22569 568.99493 552.65068 601.04582 727.9248 100克
#(基数)乘:1220.38286 1291.70601 1340.56985 1344.86291 1382.38067 1512.5377 100小时
由于这是谷歌的热门产品,我想我会添加一些我认为有用的附加选项。这个想法基本上是由员工安排一次,然后根据状态
使用data.table
library(data.table)
unique(setDT(data)[order(Employees)], by = "State")
# State Company Employees
# 1: RI E 19
# 2: AK D 24
或者,我们也可以先下订单,然后再下子集.SD
。这两种操作在最近的数据中都得到了优化。表版本和顺序似乎触发了数据。表:::forerv
,而.SD[1L]
触发了Gforce
setDT(data)[order(Employees), .SD[1L], by = State, verbose = TRUE] # <- Added verbose
# order optimisation is on, i changed from 'order(...)' to 'forder(DT, ...)'.
# i clause present and columns used in by detected, only these subset: State
# Finding groups using forderv ... 0 sec
# Finding group sizes from the positions (can be avoided to save RAM) ... 0 sec
# Getting back original order ... 0 sec
# lapply optimization changed j from '.SD[1L]' to 'list(Company[1L], Employees[1L])'
# GForce optimized j to 'list(`g[`(Company, 1L), `g[`(Employees, 1L))'
# Making each group and running j (GForce TRUE) ... 0 secs
# State Company Employees
# 1: RI E 19
# 2: AK D 24
从awesome answer中借用的另一个有趣的想法(以mult=“first”
的形式进行了一个小的修改,以处理多个匹配)是首先找到每个组的最小值,然后执行二进制连接。这样做的优点是利用了data.tablesgmin
函数(它跳过了计算开销)和二进制连接特性
tmp%切片(1),
“(plyr)ddply/which.min:”=ddply(数据、(状态)、函数(x)x[which.min(x$Employees),),
“(base)by:”=do.call(rbind,by(data,data$State,function(x)x[which.min(x$Employees),]))
#单位:毫秒
#expr最小lq平均uq最大neval cld
#(数据表).SD[which.min]:119.660
library(data.table)
library(dplyr)
library(plyr)
library(stringi)
library(microbenchmark)
set.seed(123)
N <- 1e6
data <- data.frame(State = stri_rand_strings(N, 2, '[A-Z]'),
Employees = sample(N*10, N, replace = TRUE))
DT <- copy(data)
setDT(DT)
DT2 <- copy(DT)
str(DT)
str(DT2)
microbenchmark("(data.table) .SD[which.min]: " = DT[ , .SD[which.min(Employees)], by = State],
"(data.table) .I[which.min]: " = DT[DT[ , .I[which.min(Employees)], by = State]$V1],
"(data.table) order/unique: " = unique(DT[order(Employees)], by = "State"),
"(data.table) order/.SD[1L]: " = DT[order(Employees), .SD[1L], by = State],
"(data.table) self join (on):" = {
tmp <- DT[, .(Employees = min(Employees)), by = State]
DT[tmp, on = .(State, Employees), mult = "first"]},
"(data.table) self join (setkey):" = {
tmp <- DT2[, .(Employees = min(Employees)), by = State]
setkey(tmp, State, Employees)
setkey(DT2, State, Employees)
DT2[tmp, mult = "first"]},
"(dplyr) slice(which.min): " = data %>% group_by(State) %>% slice(which.min(Employees)),
"(dplyr) arrange/distinct: " = data %>% arrange(Employees) %>% distinct(State, .keep_all = TRUE),
"(dplyr) arrange/group_by/slice: " = data %>% arrange(Employees) %>% group_by(State) %>% slice(1),
"(plyr) ddply/which.min: " = ddply(data, .(State), function(x) x[which.min(x$Employees),]),
"(base) by: " = do.call(rbind, by(data, data$State, function(x) x[which.min(x$Employees), ])))
# Unit: milliseconds
# expr min lq mean median uq max neval cld
# (data.table) .SD[which.min]: 119.66086 125.49202 145.57369 129.61172 152.02872 267.5713 100 d
# (data.table) .I[which.min]: 12.84948 13.66673 19.51432 13.97584 15.17900 109.5438 100 a
# (data.table) order/unique: 52.91915 54.63989 64.39212 59.15254 61.71133 177.1248 100 b
# (data.table) order/.SD[1L]: 51.41872 53.22794 58.17123 55.00228 59.00966 145.0341 100 b
# (data.table) self join (on): 44.37256 45.67364 50.32378 46.24578 50.69411 137.4724 100 b
# (data.table) self join (setkey): 14.30543 15.28924 18.63739 15.58667 16.01017 106.0069 100 a
# (dplyr) slice(which.min): 82.60453 83.64146 94.06307 84.82078 90.09772 186.0848 100 c
# (dplyr) arrange/distinct: 344.81603 360.09167 385.52661 379.55676 395.29463 491.3893 100 e
# (dplyr) arrange/group_by/slice: 367.95924 383.52719 414.99081 397.93646 425.92478 557.9553 100 f
# (plyr) ddply/which.min: 506.55354 530.22569 568.99493 552.65068 601.04582 727.9248 100 g
# (base) by: 1220.38286 1291.70601 1340.56985 1344.86291 1382.38067 1512.5377 100 h
ddply(df, .(State), function(x) x[which.min(x$Employees),])
# State Company Employees
# 1 AK D 24
# 2 RI E 19
data[data$Employees == ave(data$Employees, data$State, FUN=min),]
# State Company Employees
#4 AK D 24
#5 RI E 19
data[as.logical(ave(data$Employees, data$State, FUN=function(x) x==min(x))),]
#data[ave(data$Employees, data$State, FUN=function(x) x==min(x))==1,] #Variant
# State Company Employees
#4 AK D 24
#5 RI E 19
library(collapse)
library(magrittr)
data %>%
fgroup_by(State) %>%
fsummarise(Employees = fmin(Employees))