ggplot()使用scale :: percent_format()缩放产生奇怪的结果 [英] ggplot() scaling with scale::percent_format() producing strange results

问题描述

library(tidyverse)
mtcars %>% 
  count(cyl) %>% 
  mutate(prop = n / sum(n)) %>% 
  ggplot(aes(x = cyl, y = prop)) + 
  geom_point() + 
  scale_y_continuous(labels = scales::percent_format(accuracy = 5L))

如果我使用上面的scales::percent()而不是scales::percent_format(accuracy = 5L)，我会在百分比标签中获得小数位，这是我不想要的.

问题-在上述示例中， 5L的作用是什么?为什么需要使用整数5L而不是5?为什么6L将最高y值从40％更改为42％?那真是奇怪.

解决方案

首先，不需要将其精确地指定为整数(即​​5可以正常工作 ).

第二，您可以随时在R控制台中进行?scales::percent_format(免费！).这样做可以告诉您有关该功能的信息:

percent_format(
  accuracy = NULL, scale = 100, prefix = "", suffix = "%",
  big.mark = " ", decimal.mark = ".", trim = TRUE, ...
)

因此，它需要许多可能的参数，所有参数都有默认值，有些是选项(通过...).

accuracy参数的默认值为NULL.如果我们仅在功能的帮助页面上向下滚动，就会看到:

• accuracy:四舍五入到的数字，NULL用于自动猜测.

如果键入不带括号或?前缀的函数名称，则可以看到整个源代码.这样做表明它最终会调用scales::number()，其定义为:

function (x, accuracy = 1, scale = 1, prefix = "", suffix = "", 
          big.mark = " ", decimal.mark = ".", trim = TRUE, ...) {
  if (length(x) == 0) return(character())
  accuracy <- accuracy %||% precision(x)
  x <- round_any(x, accuracy/scale)
  nsmall <- -floor(log10(accuracy))
  nsmall <- min(max(nsmall, 0), 20)
  ret <- format(scale * x, big.mark = big.mark, decimal.mark = decimal.mark, 
                trim = trim, nsmall = nsmall, scientific = FALSE, ...)
  ret <- paste0(prefix, ret, suffix)
  ret[is.infinite(x)] <- as.character(x[is.infinite(x)])
  ret[is.na(x)] <- NA
  ret
}

此:

accuracy <- accuracy %||% precision(x)

说明accuracy是否不是NULL，请使用它，否则使用precision()函数进行猜测.

此后的下一行是您问题的最终答案.

library(tidyverse)
mtcars %>% 
  count(cyl) %>% 
  mutate(prop = n / sum(n)) %>% 
  ggplot(aes(x = cyl, y = prop)) + 
  geom_point() + 
  scale_y_continuous(labels = scales::percent_format(accuracy = 5L))

If I use scales::percent() above instead of scales::percent_format(accuracy = 5L) I get decimal places in my percentage labels, which I don't want.

The question - what does 5L do in my example above? Why do I need to use the integer 5L instead of 5? And why does 6L change the highest y-value from 40% to 42%? That's just plain strange.

解决方案

First, it doesn't need to be precisely specified as an integer (i.e. 5 works just fine).

Second, you can do ?scales::percent_format at any time in an R console (it's free!). Doing so tells you this about the function:

percent_format(
  accuracy = NULL, scale = 100, prefix = "", suffix = "%",
  big.mark = " ", decimal.mark = ".", trim = TRUE, ...
)

So, it takes many possible parameters all of which have defaults and some are options (via ...).

The default for the accuracy parameter is NULL. If we scroll down just a bit on the help page for the function we see:

• accuracy: Number to round to, NULL for automatic guess.

If we type the function name without parens or a ? prefix, we can see the entire source. Doing so shows that it ultimately calls scales::number() which is defined as:

function (x, accuracy = 1, scale = 1, prefix = "", suffix = "", 
          big.mark = " ", decimal.mark = ".", trim = TRUE, ...) {
  if (length(x) == 0) return(character())
  accuracy <- accuracy %||% precision(x)
  x <- round_any(x, accuracy/scale)
  nsmall <- -floor(log10(accuracy))
  nsmall <- min(max(nsmall, 0), 20)
  ret <- format(scale * x, big.mark = big.mark, decimal.mark = decimal.mark, 
                trim = trim, nsmall = nsmall, scientific = FALSE, ...)
  ret <- paste0(prefix, ret, suffix)
  ret[is.infinite(x)] <- as.character(x[is.infinite(x)])
  ret[is.na(x)] <- NA
  ret
}

This:

accuracy <- accuracy %||% precision(x)

says if accuracy is not NULL use it otherwise guess by using the precision() function.

The next line after that is the ultimate answer to your question.

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