R 如何将新摘要列的名称传递给函数中的data.table?
假设我想创建一个函数,从R中的data.table计算摘要数据集,并且我想能够以编程方式在中传递新计算变量的名称 例如:R 如何将新摘要列的名称传递给函数中的data.table?,r,data.table,R,Data.table,假设我想创建一个函数,从R中的data.table计算摘要数据集,并且我想能够以编程方式在中传递新计算变量的名称 例如: library(data.table) # generate some fake data set.seed(919) dt <- data.table(x = rnorm(50), by.var = rep(c("a", "b"), 25)) dt[, list(group.means = mean(x)), by = "by.var"] # This is wh
library(data.table)
# generate some fake data
set.seed(919)
dt <- data.table(x = rnorm(50), by.var = rep(c("a", "b"), 25))
dt[, list(group.means = mean(x)), by = "by.var"] # This is what I want
# But I want to do in a function, so I can do it repeatedly:
groupMeans <- function(out.var, by.var, dat = dt) {
return(dat[, list(out.var = mean(x)), by = by.var]) # doesn't work
}
groupMeans("group.means", "by.var") # out.var should be "group.means"
库(data.table)
#生成一些虚假数据
种子集(919)
DT 可以考虑更改函数内的列名:
groupMeans <- function(out.var, by.var, dat = dt) {
res <- dat[, list(mean(x)), by=by.var]
setnames(res, "V1", out.var)
res
}
groupMeans我们可以使用setnames
用'out.var'向量命名汇总列
groupMeans <- function(out.var, by.var, dat = dt) {
setnames(dat[, list(mean(x)), by = by.var],
length(by.var)+1L, out.var)
}
groupMeans("group.var","by.var", dt)[]
# by.var group.var
#1: a -0.1159832
#2: b 0.2910531
groupMeans承蒙,您可以使用使用setNames
创建的命名列表,如下所示:
groupMeans <- function(out.var, by.var, dat = dt) {
return(dat[, setNames(list(mean(x)), out.var), by = by.var])
}
groupMeans("group.means", "by.var")
# by.var group.means
# 1: a -0.1159832
# 2: b 0.2910531
groupMeans我会使用dat[,setNames(list(mean(x)),out.var),by=by.var]
@docendodiscimus谢谢。这是我第一次尝试的。它给了我一个错误:setnames(list(mean(x)),out.var中的错误:x不是data.table或data.frame
。不,我使用的是base R中的setnames
,而不是data.tableAha中的setnames
!真管用!看起来我很粗心,错误地使用了setnames
。谢谢你已经尝试了几乎正确的方法,或者,structure(.(mean(x)),.Names=out.var)
。。。但这更具可读性