在 R 中格式化小数位 [英] Formatting Decimal places in R

问题描述

我有一个数字，例如 1.128347132904321674821，我想在输出到屏幕(或写入文件)时只显示两位小数.如何做到这一点?

I have a number, for example 1.128347132904321674821 that I would like to show as only two decimal places when output to screen (or written to a file). How does one do that?

x <- 1.128347132904321674821

使用:

options(digits=2)

已被建议作为可能的答案.有没有办法在脚本中指定它以供一次性使用?当我将它添加到我的脚本中时，它似乎并没有做任何不同的事情，而且我对大量重新键入以格式化每个数字不感兴趣(我正在自动化一个非常大的报告).

Has been suggested as a possible answer. Is there a way to specify this within a script for one-time use? When I add it to my script it doesn't seem to do anything different and I'm not interested in a lot of re-typing to format each number (I'm automating a very large report).

--

答案:round(x,digits=2)

Answer: round(x, digits=2)

推荐答案

背景: 本页建议的一些答案(例如，signif、options(digits=...)) 不保证为任意数字显示一定数量的小数.我认为这是 R 中的一个设计功能，良好的科学实践涉及根据 原则显示一定数量的数字有效数字".然而，在许多领域(例如，APA 风格，商业报告)格式要求规定显示一定数量的小数位.这样做通常是为了一致性和标准化目的，而不是关注有效数字.

Background: Some answers suggested on this page (e.g., signif, options(digits=...)) do not guarantee that a certain number of decimals are displayed for an arbitrary number. I presume this is a design feature in R whereby good scientific practice involves showing a certain number of digits based on principles of "significant figures". However, in many domains (e.g., APA style, business reports) formatting requirements dictate that a certain number of decimal places are displayed. This is often done for consistency and standardisation purposes rather than being concerned with significant figures.

解决方案:

以下代码正好显示了数字 x 的两位小数.

The following code shows exactly two decimal places for the number x.

format(round(x, 2), nsmall = 2)

例如:

format(round(1.20, 2), nsmall = 2)
# [1] "1.20"
format(round(1, 2), nsmall = 2)
# [1] "1.00"
format(round(1.1234, 2), nsmall = 2)
# [1] "1.12"

更通用的函数如下，其中 x 是数字，k 是要显示的小数位数.trimws 删除任何前导空格，如果您有数字向量，这可能很有用.

A more general function is as follows where x is the number and k is the number of decimals to show. trimws removes any leading white space which can be useful if you have a vector of numbers.

specify_decimal <- function(x, k) trimws(format(round(x, k), nsmall=k))

例如，

specify_decimal(1234, 5)
# [1] "1234.00000"
specify_decimal(0.1234, 5)
# [1] "0.12340"

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