gganimate与geom_bar有关? [英] gganimate issue with geom_bar?

问题描述

自从大卫·罗宾逊(David Robinson)发布他的gganimate软件包以来，我一直羡慕和钦佩于Twitter上出现的各种ggplot动画，并认为自己会自己玩.使用geom_bar时，我的gganimate有问题.希望下面的示例演示该问题.

I've been looking with envy and admiration at the various ggplot animations appearing on twitter since David Robinson released his gganimate package and thought I'd have a play myself. I am having an issue with gganimate when using geom_bar. Hopefully the following example demonstrates the problem.

首先为可重现的示例生成一些数据:

First generate some data for a reproducible example:

df <- data.frame(x = c(1, 2, 1, 2),
                 y = c(1, 2, 3, 4),
                 z = c("A", "A", "B", "B"))

为演示我要执行的操作，我认为绘制由z刻面的普通ggplot很有用.我正在尝试让gganimate产生一个在这2个图之间循环的gif.

To demonstrate what I'm trying to do I thought it would be useful to plot an ordinary ggplot, facetted by z. I'm trying to get gganimate to produce a gif that cycles between these 2 plots.

ggplot(df, aes(x = x, y = y)) +
   geom_bar(stat = "Identity") +
   facet_grid(~z)

但是当我使用gganimate时，B的图表现很奇怪.在第二帧中，小节从第一帧的小节结束处开始，而不是从原点开始.好像是堆积的条形图.

But when I use gganimate the plot for B behaves oddly. In the second frame the bars start at the values that the first frame's bars finish at, rather than starting at the origin. As if it was a stacked bar chart.

p <- ggplot(df, aes(x = x, y = y, frame = z)) +
   geom_bar(stat = "Identity") 
gg_animate(p)

顺便说一句，当使用geom_point尝试相同的绘图时，一切都会按预期进行.

Incidentally when trying the same plot with geom_point everything works as expected.

q <- ggplot(df, aes(x = x, y = y, frame = z)) +
    geom_point() 
gg_animate(q)

我试图发布一些图像，但是显然我没有足够的声誉，因此，我希望没有它们就有意义.这是一个错误，还是我缺少什么?

I tried to post some images, but apparently I don't have sufficient reputation, so I hope it makes sense without them. Is this a bug, or am I missing something?

预先感谢

托马斯

推荐答案

原因是没有条面，条形图是堆叠在一起的.使用position = "identity":

The reason is that without faceting, the bars are stacked. Use position = "identity":

p <- ggplot(df, aes(x = x, y = y, frame = z)) +
  geom_bar(stat = "Identity", position = "identity") 
gg_animate(p)

为了避免在这种情况下造成混淆，将frame替换为fill(或colour，具体取决于您所使用的几何图形)更为有用:

In order to avoid confusion in situations like this, it is much more useful to replace frame by fill (or colour, depending on the geom you are using`):

p <- ggplot(df, aes(x = x, y = y, fill = z)) +
  geom_bar(stat = "Identity") 
p

用frame替换fill时绘制的两个图完全对应于排他地一次绘制一种颜色.

The two plots that are drawn, when you replace fill by frame correspond exactly to exclusively drawing one of the colours at a time.

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