我使用这个变体来强制打印K位小数点后数位:

# format numeric value to K decimal places
formatDecimal <- function(x, k) format(round(x, k), trim=T, nsmall=k)

小数点后两位假设你想保持后面的0

sprintf(5.5, fmt = '%#.2f')

这给了

[1] "5.50"

正如下面@mpag提到的，似乎R有时会给出意想不到的值，而舍入方法，例如sprintf(5.5550, fmt='%#.2f')给出5.55，而不是5.56

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:

下面的代码显示了数字x的小数点后两位。

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"

一个更一般的函数如下所示，其中x是数字，k是要显示的小数的数量。Trimws删除任何前导空白，如果你有一个数字向量，这可能是有用的。

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"

替代方案的讨论:

formatC答案和sprintf答案工作得相当好。但在某些情况下，它们会显示负0，这可能是不需要的。也就是说,

formatC(c(-0.001), digits = 2, format = "f")
# [1] "-0.00"
sprintf(-0.001, fmt = '%#.2f')
# [1] "-0.00"

一个可能的解决方法如下:

formatC(as.numeric(as.character(round(-.001, 2))), digits = 2, format = "f")
# [1] "0.00" 

这是我从单位到百万的方法。 Digits参数让我调整有效值(整数+小数)的最小数量。你可以先调整里面的十进制四舍五入。

number <-function(number){
  result <- if_else(
    abs(number) < 1000000,
    format(
      number, digits = 3,
      big.mark = ".",
      decimal.mark = ","
    ),
    paste0(
      format(
        number/1000000,
        digits = 3,
        drop0trailing = TRUE,
        big.mark = ".",
        decimal.mark = ","
      ),
      "MM"
    )
  )
  # result <- paste0("$", result)
  return(result)
}

我写了这个可以改进的函数，但看起来在极端情况下工作得很好。例如，在0.9995的情况下，投票正确的答案是1.00，这是不正确的。我在这个数没有小数的情况下使用这个解。

round_correct <- function(x, digits, chars = TRUE) {
  if(grepl(x = x, pattern = "\\.")) {
    y <- as.character(x)
    pos <- grep(unlist(strsplit(x = y, split = "")), pattern = "\\.", value = FALSE)
    if(chars) {
      return(substr(x = x, start = 1, stop = pos + digits))
    }
    return(
      as.numeric(substr(x = x, start = 1, stop = pos + digits))
    )
  } else {
    return(
      format(round(x, 2), nsmall = 2)
    )
  }
}

例子:

round_correct(10.59648, digits = 2)
[1] "10.59"
round_correct(0.9995, digits = 2)
[1] "0.99"
round_correct(10, digits = 2)
[1] "10.00"

函数formatC()可用于将数字格式化到小数点后两位。即使结果值包含后面的零，此函数也会给出两位小数。