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在 data.table 中分组后查找统计信息

[英]Finding statistics after grouping in data.table

 原文  2021-10-27 12:24:00  6   2    r/ data.table

问题描述

I had a small question in regards to data.table.我有一个关于 data.table 的小问题。 Since i'm not so good at it i'm not quite sure how I can do this in data.table.因为我不太擅长它，所以我不太确定如何在 data.table 中做到这一点。

Basically I have 3 columns and want to group by the first two columns ( key and date ) and then for each key and each date, find the maximum and minimum that occurred in the third column ( fare)基本上我有 3 列，想按前两列（键和日期）分组，然后对于每个键和每个日期，找到第三列（票价）中出现的最大值和最小值

I tried doing this but it gives me an error我试过这样做，但它给了我一个错误

flights[, c("max_day", "min_day") := unlist(lapply(gross_fare, findr)), by = c("key", "created_date")]


Error in `[.data.table`(flights, , `:=`(c("max_day", "min_day"), unlist(lapply(gross_fare,  : 
  Supplied 18 items to be assigned to group 1 of size 9 in column 'max_day'. The RHS length must either be 1 (single values are ok) or match the LHS length exactly. If you wish to 'recycle' the RHS please use rep() explicitly to make this intent clear to readers of your code.

findr is a function which just finds the max and min ie findr 是一个函数，它只找到最大值和最小值，即

findr <- function(x) {list(max = max(x), min = min(x)}

I've done what I want to do in dplyr and I'll attach the code for that, but since i have millions of rows, dplyr eats up my ram so data.table would help我已经在 dplyr 中完成了我想做的事情，我会附上代码，但是由于我有数百万行，dplyr 吃光了我的内存，因此 data.table 会有所帮助

test <- flights %>%
  select(key, created_date, gross_fare) %>%
  group_by(key, created_date) %>%
  summarise(
            max_day = max(gross_fare),
            min_day = min(gross_fare),
            diff = max_day - min_day) %>%
  arrange(created_date)

I've put the dput output if anyone wants to use that If anyone can help that'd be great, thank you :)如果有人想使用它，我已经把 dput 输出放在那里，如果有人能提供帮助，那就太好了，谢谢:)

structure(list(key = c("LHE_KHI_LHE+KHI_PA-405_15.0_1", "KHI_ISB_KHI+ISB_PK-370_20.0_0", 
"LHE_KHI_LHE+KHI_PK-307_20.0_0", "ISB_KHI_ISB+KHI_PF-124_20.0_1", 
"LHE_KHI_LHE+KHI_PK-307_20.0_0", "LHE_KHI_LHE+KHI_PA-405_15.0_1", 
"KHI_LHE_KHI+LHE_PK-304_20.0_0", "KHI_ISB_KHI+ISB_PA-204_15.0_1", 
"ISB_KHI_ISB+KHI_PA-207_15.0_1", "KHI_ISB_KHI+ISB_PA-200_20.0_1", 
"KHI_LHE_KHI+LHE_PK-304_40.0_0", "ISB_KHI_ISB+KHI_PA-201_35.0_1", 
"ISB_KHI_ISB+KHI_ER-501_20.0_1", "KHI_LHE_KHI+LHE_PF-145_20.0_2", 
"KHI_ISB_KHI+ISB_PA-204_20.0_1", "LHE_KHI_LHE+KHI_PA-401_0.0_0", 
"ISB_KHI_ISB+KHI_PK-309_40.0_0", "KHI_ISB_KHI+ISB_PF-123_20.0_2", 
"ISB_KHI_ISB+KHI_PA-205_15.0_1", "LHE_KHI_LHE+KHI_PF-142_0.0_0", 
"ISB_KHI_ISB+KHI_PA-223_15.0_1", "ISB_KHI_ISB+KHI_PF-126_20.0_2", 
"ISB_KHI_ISB+KHI_PK-309_20.0_0", "KHI_ISB_KHI+ISB_PF-121_20.0_2", 
"ISB_KHI_ISB+KHI_PK-373_20.0_0", "KHI_LHE_KHI+LHE_PF-145_20.0_2", 
"KHI_LHE_KHI+LHE_PA-402_15.0_1", "LHE_KHI_LHE+KHI_PA-407_20.0_1", 
"KHI_ISB_KHI+ISB_PK-308_40.0_0", "KHI_LHE_KHI+LHE_PF-145_20.0_2", 
"LHE_KHI_LHE+KHI_PF-144_0.0_0", "ISB_KHI_ISB+KHI_PK-369_40.0_0", 
"ISB_KHI_ISB+KHI_PF-124_20.0_2", "KHI_ISB_KHI+ISB_PA-204_15.0_1", 
"KHI_ISB_KHI+ISB_PA-200_15.0_1", "ISB_KHI_ISB+KHI_PF-124_20.0_1", 
"KHI_ISB_KHI+ISB_PK-300_20.0_0", "ISB_KHI_ISB+KHI_PF-122_20.0_2", 
"KHI_ISB_KHI+ISB_PK-368_20.0_0", "KHI_ISB_KHI+ISB_PA-204_15.0_1", 
"ISB_KHI_ISB+KHI_ER-503_20.0_1", "ISB_KHI_ISB+KHI_PA-209_15.0_1", 
"KHI_ISB_KHI+ISB_PK-308_40.0_0", "ISB_KHI_ISB+KHI_PF-124_20.0_1", 
"ISB_KHI_ISB+KHI_PK-301_40.0_0", "KHI_LHE_KHI+LHE_PA-408_35.0_1", 
"LHE_KHI_LHE+KHI_PF-144_20.0_2", "KHI_ISB_KHI+ISB_PF-121_20.0_2", 
"KHI_ISB_KHI+ISB_PA-204_35.0_1", "ISB_KHI_ISB+KHI_PK-309_40.0_0", 
"ISB_KHI_ISB+KHI_PA-223_20.0_1", "KHI_ISB_KHI+ISB_PA-206_35.0_1", 
"LHE_KHI_LHE+KHI_PF-142_32.0_1", "LHE_KHI_LHE+KHI_PF-142_20.0_1", 
"KHI_ISB_KHI+ISB_PF-123_20.0_2", "ISB_KHI_ISB+KHI_PA-209_15.0_1", 
"KHI_ISB_KHI+ISB_PA-204_35.0_1", "ISB_KHI_ISB+KHI_PA-201_20.0_1", 
"KHI_ISB_KHI+ISB_PK-368_20.0_0", "ISB_KHI_ISB+KHI_PA-205_20.0_1", 
"KHI_ISB_KHI+ISB_PF-121_20.0_1", "ISB_KHI_ISB+KHI_PF-124_20.0_1", 
"ISB_KHI_ISB+KHI_PA-205_15.0_1", "KHI_LHE_KHI+LHE_PF-145_20.0_2", 
"KHI_LHE_KHI+LHE_PA-406_35.0_1", "KHI_ISB_KHI+ISB_PK-308_20.0_0", 
"LHE_KHI_LHE+KHI_PA-401_20.0_1", "LHE_KHI_LHE+KHI_PA-401_15.0_1", 
"KHI_ISB_KHI+ISB_PA-204_35.0_1", "KHI_LHE_KHI+LHE_PA-406_35.0_1", 
"KHI_ISB_KHI+ISB_PA-206_35.0_1", "KHI_ISB_KHI+ISB_PF-121_20.0_1", 
"ISB_KHI_ISB+KHI_PA-205_20.0_1", "LHE_KHI_LHE+KHI_PF-142_20.0_1", 
"LHE_KHI_LHE+KHI_PF-146_20.0_2", "LHE_KHI_LHE+KHI_PA-401_35.0_1", 
"ISB_KHI_ISB+KHI_PA-209_15.0_1", "ISB_KHI_ISB+KHI_PK-301_40.0_0", 
"ISB_KHI_ISB+KHI_PA-205_35.0_1", "KHI_LHE_KHI+LHE_PA-406_15.0_1", 
"KHI_ISB_KHI+ISB_PF-123_20.0_1", "ISB_KHI_ISB+KHI_PA-201_35.0_1", 
"KHI_ISB_KHI+ISB_PK-300_40.0_0", "KHI_LHE_KHI+LHE_PA-402_35.0_1", 
"ISB_KHI_ISB+KHI_ER-505_20.0_1", "ISB_KHI_ISB+KHI_PF-122_20.0_2", 
"ISB_KHI_ISB+KHI_PA-207_15.0_1", "KHI_LHE_KHI+LHE_PA-404_35.0_1", 
"KHI_ISB_KHI+ISB_PF-123_20.0_1", "ISB_KHI_ISB+KHI_ER-503_20.0_1", 
"ISB_GIL_ISB+GIL_PK-605_20.0_0", "KHI_ISB_KHI+ISB_PF-123_20.0_1", 
"KHI_ISB_KHI+ISB_PA-200_15.0_1", "ISB_KHI_ISB+KHI_PF-122_20.0_2", 
"KHI_LHE_KHI+LHE_PA-404_35.0_1", "ISB_KHI_ISB+KHI_PF-122_20.0_2", 
"PEW_KHI_PEW+KHI_PF-152_20.0_1", "LHE_KHI_LHE+KHI_PK-303_20.0_0", 
"KHI_ISB_KHI+ISB_PA-222_35.0_1", "ISB_KHI_ISB+KHI_PF-124_20.0_1"
), created_date = c("2021-04-20", "2021-05-27", "2021-02-13", 
"2021-08-14", "2021-08-11", "2021-08-21", "2021-01-26", "2021-08-21", 
"2021-05-24", "2021-09-15", "2021-06-05", "2021-07-19", "2021-09-29", 
"2021-07-02", "2021-08-10", "2021-01-04", "2021-07-15", "2021-07-14", 
"2021-08-13", "2021-01-11", "2021-09-13", "2021-09-20", "2021-05-27", 
"2021-02-20", "2021-08-15", "2021-07-27", "2021-08-26", "2021-09-15", 
"2021-08-02", "2021-06-25", "2021-05-15", "2021-08-26", "2021-07-30",
"2021-06-27", "2021-08-07", "2021-03-19", "2021-03-02", "2021-06-06", 
"2021-08-15", "2021-06-27", "2021-09-19", "2021-07-28", "2021-08-09", 
"2021-08-16", "2021-09-09", "2021-06-04", "2021-08-12", "2021-05-15", 
"2021-07-26", "2021-05-27", "2021-08-12", "2021-08-02", "2021-01-26", 
"2021-04-20", "2021-08-26", "2021-08-26", "2021-03-21", "2021-01-09", 
"2021-04-23", "2021-01-04", "2021-08-13", "2021-06-22", "2021-05-31", 
"2021-08-18", "2021-06-16", "2021-08-14", "2021-08-10", "2021-06-16", 
"2021-04-08", "2021-05-20", "2021-06-22", "2021-04-20", "2021-01-05", 
"2021-02-27", "2021-07-07", "2021-03-26", "2021-08-16", "2021-05-01", 
"2021-07-31", "2021-06-14", "2021-06-16", "2021-03-25", "2021-09-14", 
"2021-06-06", "2021-09-02", "2021-08-06", "2021-07-18", "2021-02-28", 
"2021-04-28", "2021-09-19", "2021-08-25", "2021-06-17", "2021-06-07", 
"2021-06-17", "2021-07-07", "2021-08-23", "2021-07-09", "2021-07-19", 
"2021-07-14", "2021-05-21"), gross_fare = c(7796, 7427, 11504, 
6870, 6580, 14945, 8697, 7524, 7124, 6785, 11858, 7524, 11500, 
9525, 6785, 8739, 8200, 13560, 9045, 7400, 7524, 12500, 7458, 
14000, 6570, 9525, 6220, 10545, 8310, 7900, 7820, 8410, 11285, 
19892, 6810, 9800, 11441, 11900, 6570, 13592, 11500, 8300, 20380, 
8525, 7340, 9707, 7870, 10655, 10545, 11798, 14645, 10545, 8650, 
8650, 7870, 12945, 10799, 10227, 6765, 10227, 20120, 11045, 9403, 
7870, 7124, 6570, 6810, 6531, 8605, 7124, 11072, 7390, 10227, 
13435, 10530, 12280, 18945, 11147, 10545, 6531, 6620, 10799, 
18480, 32702, 5606, 13560, 23895, 8027, 9655, 11500, 11990, 6620, 
9403, 7620, 14645, 19105, 9000, 6440, 12645, 8025)), row.names = c(NA, 
-100L), class = c("data.table", "data.frame"), .internal.selfref = <pointer: 0x000001eb382c1ef0>)
>

2 个解决方案

解决方案1
 1  2021-10-27 12:41:19

I guess this line of code should do the job:我想这行代码应该可以完成这项工作：

library(data.table)

flights[,  .(min_day = min(gross_fare), max_day = max(gross_fare), diff = max(gross_fare) - min(gross_fare)), by = .(key, created_date)][]

解决方案2
 0  2021-10-27 13:02:56

Since the function findr returns a list, there's no need to complicate things:由于函数findr返回一个列表，因此无需将事情复杂化：

findr <- function(x) {list(max = max(x), min = min(x))}

flights[, c("max_day", "min_day") := findr(gross_fare), by = list(key, created_date)][]

To also return the difference between max and min , use要同时返回max和min之间的差异，请使用

findr2 <- function(x) {
  list(max = max(x), min = min(x), diff = diff(range(x)))
}

flights[, c("max_day", "min_day", "diff_day") := findr2(gross_fare), by = list(key, created_date)][]

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