geom_jitter的高度/宽度参数与日志刻度交互

Question

在探索一些数据的时候发现了这一点，这感觉像是意外的行为，所以我想我会发帖。

geom_jitter采用高度/宽度参数来表示抖动的宽度，默认值为40%。当添加日志刻度时，这40%似乎应用于原始值。但是，如果要调整此参数，则在日志转换后应用该值。

这可以如下所示：

library(ggplot2)
library(patchwork)

set.seed(1)
dat <- data.frame(x=round(rlnorm(2000)), y=round(rlnorm(2000)))


# THESE TWO PLOTS ARE THE SAME
# with jitter
p1 <- ggplot(dat, aes(x,y)) + geom_jitter(alpha=.1) +
  labs(title='regular scale, jitter with default height/width',
       subtitle = '')
# with jitter, and explicit (but same as default) jitter size
p2 <- ggplot(dat, aes(x,y)) + geom_jitter(alpha=.1, height=.4, width=.4) +
  labs(title='regular scale, jitter with 40% height/width',
       subtitle = '<== same as that')


# THESE TWO PLOTS ARE NOT THE SAME
# with jitter and log/log scale
p3 <- ggplot(dat, aes(x,y)) + geom_jitter(alpha=.1) +
  scale_x_log10() + scale_y_log10() +
  labs(title='log scale, jitter with default height/width',
       subtitle = '')

# with jitter and log/log scale, and explicit (but same as default) jitter size
p4 <- ggplot(dat, aes(x,y)) + geom_jitter(alpha=.1, height=.4, width=.4) +
  scale_x_log10() + scale_y_log10()  +
  labs(title='log scale, jitter with 40% height/width',
       subtitle = '<== NOT the same as that')

(p1 + p2) / (p3 + p4)

​

​

这是预期的行为吗？

如果我想调整基础值的抖动宽度，而不是日志转换值的抖动宽度，该怎么办？

Answer 1

这是个不错的机会！我想这是个文档问题--还不够清楚。抖动是而不是40%，它是数据分辨率的40%的。

在ggplot2:::PositionJitter$setup_params中，您可以看到应用了ggplot2:::resolution函数，其结果乘以0.4

list(width = self$width %||% (resolution(data$x, zero = FALSE) * 
    0.4), height = self$height %||% (resolution(data$y, zero = FALSE) * 
    0.4), seed = self$seed)

因此，您需要做的是在将值传递给ggplot2:::resolution /height之前应用width/height

geom_jitter(
  width = ggplot2:::resolution(log10(dat$x), FALSE) * 0.4,
  height = ggplot2:::resolution(log10(dat$y), FALSE) * 0.4,
)

​

​

所有代码：

ggplot(dat, aes(x, y)) + 
  geom_jitter(
    width = ggplot2:::resolution(log10(dat$x), FALSE) * 0.4,
    height = ggplot2:::resolution(log10(dat$y), FALSE) * 0.4,
  ) +
  scale_x_log10() +
  scale_y_log10() +
  labs(title = 'Scale when resolution is applied')