连接极线ggplot图中的间隙 [英] Join gap in polar line ggplot plot

问题描述

当ggplot用极坐标绘制线图时，它在最高x值和最低x值(下面的Dec和Jan)之间留有间隙，而不是缠绕成螺旋状.我怎样才能继续做下去并缩小差距?

When ggplot makes a line plot with polar coordinates, it leaves a gap between the highest and lowest x-values (Dec and Jan below) instead of wrapping around into a spiral. How can I continue the line and close that gap?

特别是，我想使用几个月作为我的x轴，但是在一条循环线中绘制多年的数据.

In particular, I want to use months as my x-axis, but plot multiple years of data in one looping line.

代表:

library(ggplot2)

# three years of monthly data
df <- expand.grid(month = month.abb, year = 2014:2016)
df$value <- seq_along(df$year)

head(df)
##   month year value
## 1   Jan 2014     1
## 2   Feb 2014     2
## 3   Mar 2014     3
## 4   Apr 2014     4
## 5   May 2014     5
## 6   Jun 2014     6

ggplot(df, aes(month, value, group = year)) + 
    geom_line() + 
    coord_polar()

推荐答案

这是一个有点棘手的选项:

Here's a somewhat-hacky option:

# make a data.frame of start values end values should continue to
bridges <- df[df$month == 'Jan',]
bridges$year <- bridges$year - 1    # adjust index to align with previous group
bridges$month <- NA    # set x value to any new value

       # combine extra points with original
ggplot(rbind(df, bridges), aes(month, value, group = year)) + 
    geom_line() + 
    # close gap by removing expansion; redefine breaks to get rid of "NA/Jan" label
    scale_x_discrete(expand = c(0,0), breaks = month.abb) + 
    coord_polar()

显然，添加额外的数据点并不理想，因此可能存在一个更优雅的答案.

Obviously adding extra data points is not ideal, though, so maybe a more elegant answer exists.

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