将值分配到特定范围 [英] Assign value to specific range

问题描述

我有一个简单的问题要弄清楚：

I have an easy question to figure out:

value
1000
2500
5080
10009

我要指定值到一个间隔：

value    Range
1000     0-1000
2500     1001-5000
5080     5001-10000
10009    10001-20000

我尝试以下操作：

dt[, Range := ifelse(value < 1001, "0-1000", ifelse(1000 < value < 5001, "1001-5000", ifelse(5000 < value < 10001, "5001-10000", "10001-20000")))

但是，我得到了错误： dt [中出现意外的'<'，范围：= ifelse（值< 1001， 0-1000，ifelse （1000< value<

有什么帮助吗？

编辑：

这个问题并不是在寻求将连续变量转换为因子的最佳方法，而是在寻求可重现示例的调试帮助：

This question is not asking for the best way to convert a continuous variable to a factor. It is asking for debugging help with the reproducible example:

library(data.table)
dt <- data.table(value = c(1000, 2500, 5080, 10009))
dt[, Range := ifelse(value < 1001, "0-1000", ifelse(1000 < value < 5001, "1001-5000", ifelse(5000 < value < 10001, "5001-10000", "10001-20000")))
# produces the error above

推荐答案

）错误，则表示其含义。与python不同，R无法解释 1000<值< 5001 。相反，您需要使用 1000<价值和值< 5001

Like many (some) errors, it means what it says. Unlike python, R can't interpret 1000 < value < 5001. Instead you need to use 1000 < value & value < 5001

library(data.table)
dt <- data.table(value = c(1000, 2500, 5080, 10009))
dt[, Range := ifelse(value < 1001, "0-1000", ifelse(1000 < value & value < 5001, "1001-5000", ifelse(5000 < value & value < 10001, "5001-10000", "10001-20000")))]
dt
   value       Range
1:  1000      0-1000
2:  2500   1001-5000
3:  5080  5001-10000
4: 10009 10001-20000

正如@akrun提到的那样，您可能会有一个更好的选择。例如：

As @akrun mentioned, you may be better off with a factor. Here's an example:

dt[, Range := cut(value, breaks = c(0, 1001, 5001, 10001, 20001), labels = c("0-1000", "1001-5000", "5001-10000", "10001-20000"))]

这会产生一个显示相同方式的data.table，但是提取 Range 列将为您提供一个与范围。

This produces a data.table that displays the same way, but extracting the Range column will give you a factor corresponding to the ranges.

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