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r - 在带有 data.table 的函数中使用 by

转载 作者:行者123 更新时间:2023-12-04 15:05:38 24 4
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我写了一个小函数来通过一个离散变量聚合多个列:

library(data.table)

onewayfn <- function(df, x, weight = NULL, displacement = NULL, by = NULL){
.x <- deparse(substitute(x))
.weight <- deparse(substitute(weight))
.displacement <- deparse(substitute(displacement))
.by <- deparse(substitute(by)) # Does not work with multiple variables!

cols <- c(.weight, .displacement)
cols <- cols[cols != "NULL"]

.xby <- c(.x, .by)
.xby <- .xby[.xby != "NULL"]

data.table::data.table(df)[, lapply(.SD, sum, na.rm = TRUE), by = .xby, .SDcols = cols][]
}

返回变量 wtdisp 的总和(按 cylam 分组):

onewayfn(mtcars, cyl, weight = wt, displacement = disp, by = am)

#> cyl am wt disp
#> 1: 6 1 8.265 465.0
#> 2: 4 1 16.338 748.9
#> 3: 6 0 13.555 818.2
#> 4: 8 0 49.249 4291.4
#> 5: 4 0 8.805 407.6
#> 6: 8 1 6.740 652.0

以下也返回正确的结果:


onewayfn(mtcars, cyl, weight = wt, displacement = disp)
#> cyl wt disp
#> 1: 6 21.820 1283.2
#> 2: 4 25.143 1156.5
#> 3: 8 55.989 4943.4

但是,如果我将多个变量添加到 by 中,该函数将返回错误:

onewayfn(mtcars, cyl, weight = wt, displacement = disp, by = list(am,vs))

我想获得与上面相同的结果,但现在按 cylamvs 分组。我如何重写 onewayfn() 来执行此操作?

最佳答案

我们可以将 by 作为字符串向量传递

onewayfn <- function(df, x, weight = NULL, displacement = NULL, by = NULL){
.x <- deparse(substitute(x))
.weight <- deparse(substitute(weight))
.displacement <- deparse(substitute(displacement))
#.by <- deparse(substitute(by)) # Does not work with multiple variables!

cols <- c(.weight, .displacement)
cols <- cols[cols != "NULL"]

.xby <- c(.x, by)
.xby <- .xby[.xby != "NULL"]

data.table::data.table(df)[, lapply(.SD, sum, na.rm = TRUE), by = .xby, .SDcols = cols][]
}

-测试

onewayfn(mtcars, cyl, weight = wt, displacement = disp, by = c("am","vs"))

# cyl am vs wt disp
#1: 6 1 0 8.265 465.0
#2: 4 1 1 14.198 628.6
#3: 6 0 1 13.555 818.2
#4: 8 0 0 49.249 4291.4
#5: 4 0 1 8.805 407.6
#6: 4 1 0 2.140 120.3
#7: 8 1 0 6.740 652.0

或者另一种选择是evaluate一个字符串

newayfn <- function(df, x, weight = NULL, displacement = NULL, by = NULL){

dfname <- deparse(substitute(df))
.x <- deparse(substitute(x))
.weight <- deparse(substitute(weight))
.displacement <- deparse(substitute(displacement))
.by <- deparse(substitute(by)) # Does not work with multiple variables!


cols <- c(.weight, .displacement)
cols <- cols[cols != "NULL"]
cols <- paste(dQuote(cols, FALSE), collapse=",")
cols <- glue::glue("c({cols})")
.by <- gsub("list\\(|\\)", "", .by)
.xby <- c(.x, .by)
.xby <- .xby[.xby != "NULL"]
.xby1 <- paste0("c(", gsub("(\\w+)", "'\\1'", toString(.xby)), ")")
str1 <- glue::glue('data.table::data.table({dfname})[, lapply(.SD, sum, na.rm = TRUE), by = {.xby1}, .SDcols = {cols}][]')
print(str1)
eval(parse(text = str1))
}

-测试

onewayfn(mtcars, cyl, weight = wt, displacement = disp, by = list(am, vs))
#data.table::data.table(mtcars)[, lapply(.SD, sum, na.rm = TRUE), by = c('cyl', 'am', 'vs'), .SDcols = c("wt","disp")][]
# cyl am vs wt disp
#1: 6 1 0 8.265 465.0
#2: 4 1 1 14.198 628.6
#3: 6 0 1 13.555 818.2
#4: 8 0 0 49.249 4291.4
#5: 4 0 1 8.805 407.6
#6: 4 1 0 2.140 120.3
#7: 8 1 0 6.740 652.0

onewayfn(mtcars, cyl, weight = wt, displacement = disp, by = am)
#data.table::data.table(mtcars)[, lapply(.SD, sum, na.rm = TRUE), by = c('cyl', 'am'), .SDcols = c("wt","disp")][]
# cyl am wt disp
#1: 6 1 8.265 465.0
#2: 4 1 16.338 748.9
#3: 6 0 13.555 818.2
#4: 8 0 49.249 4291.4
#5: 4 0 8.805 407.6
#6: 8 1 6.740 652.0

关于r - 在带有 data.table 的函数中使用 by,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/66198357/

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