如何检测裸变量或字符串 [英] How to detect if bare variable or string

问题描述

我正在尝试编写绘图功能，您可以在其中传递裸列名称以选择要绘制的列.我还希望能够指定一个字符串作为颜色.

I am trying to write a plotting function where you can pass bare column names to select which columns are plotted. I would like also to be able to specify a string as the color.

我发现如果要将字符串传递给aes_string，则需要使用shQuote.现在我的问题是找出是否传递了裸名或字符串.我该怎么办?

I have found that I need to use shQuote if I want to pass a string to aes_string. Now my problem is to figure out if a bare name or a string was passed. How would I do this?

dat <- data.frame(
    time = factor(c("Lunch","Dinner"), levels=c("Lunch","Dinner")),
    total_bill = c(14.89, 17.23)
)



plot_it <- function(dat, x,y, fill){
    require(rlang)
    require(ggplot2)

    x <- enquo(x)
    y <- enquo(y)
    fill <- enquo(fill)

    xN <- quo_name(x)
    yN <- quo_name(y)
    fillN <- quo_name(fill)

ggplot(data=dat, aes_string(x=xN, y=yN, fill=fillN)) +
    geom_bar(stat="identity")

}

这有效:

plot_it(dat, time, total_bill, time)

这不是:

plot_it(dat, time, total_bill, "grey")

请注意，这需要最新版本的rlang和ggplot2.

Note that this requires the newest versions of rlang and ggplot2.

推荐答案

从您的答案和

解决您原来的问题

像Eumenedies一样防止不必要的传说

提供可以无误添加到的ggplot对象

根据Eumenedies的建议使用更合适的 geom_col

主要技巧是，如果 fill 不是情节中的一个因素，则希望将其放在 aes / aes_string 之外阻止.

The main trick is that, if fill isn't a factor in the plot, you want it outside of the aes / aes_string block.

plot_it <- function(dat, x, y, fill) {

  lst <- as.list(match.call())

  xN <- quo_name(enquo(x))
  yN <- quo_name(enquo(y))

  if(is.character(lst$fill)) {
    p <- ggplot(data=dat, aes_string(x=xN, y=yN)) +
      geom_col(fill = fill)
  } else {
    p <- ggplot(data=dat, aes_string(x=xN, y=yN, fill = quo_name(enquo(fill)))) +
      geom_col()
  }

  return(p)
}

plot_it(dat, time, total_bill, time)
plot_it(dat, time, total_bill, "blue")
plot_it(dat, time, total_bill, "blue") + geom_point()

您可以通过将第二种情况下的 fill 美观性移至 geom_col 调用来缩短 if 块，但这会扩展为如果添加更多的几何图形，则采用另一种方法.

You could make the if block shorter by moving the fill aesthetic in the second case to the geom_col call, but that will extend in a different way if you add more geoms.

此外，一旦将 ggplot 更新为支持 rlang ，最好避免使用 aes_string 和 quo_name 组合，只需使用 !! fill .

Also, once ggplot is updated to support rlang, it would be cleaner to avoid aes_string and quo_name combination and just use !!fill.

请注意，假设存在 fill 因素，如果它总是与 x 因素相同，那么拥有一个版本可能更有意义其中 fill 是可选参数.如果包含该参数，则只会覆盖默认的每个因数颜色.

Note that, assuming that the fill factor exists, if it's always going to be the same as the x factor, it would probably make more sense to have a version where fill is an optional argument. You would only overwrite the default per-factor color if the argument is included.

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