从ggplot提取数据 [英] Extract data from a ggplot

问题描述

我已经从数据框中使用ggplot2 geom_histogram进行了绘制.请参阅下面的示例，并链接到ggplot直方图

I have made a plot using ggplot2 geom_histogram from a data frame. See sample below and link to the ggplot histogram Need to label each geom_vline with the factors using a nested ddply function and facet wrap

我现在需要制作一个数据框，其中包含用于生成上述ggplot的汇总数据.

I now need to make a data frame that contains the summarized data used to generate the ggplot above.

Sector2 Family  Year    Length
BUN Acroporidae 2010    332.1300496
BUN Poritidae   2011    141.1467966
BUN Acroporidae 2012    127.479
BUN Acroporidae 2013    142.5940556
MUR Faviidae    2010    304.0405
MUR Faviidae    2011    423.152
MUR Pocilloporidae  2012    576.0295
MUR Poritidae   2013    123.8936667
NTH Faviidae    2010    60.494
NTH Faviidae    2011    27.427
NTH Pocilloporidae  2012    270.475
NTH Poritidae   2013    363.4635

推荐答案

要获取实际绘制的值，可以使用函数ggplot_build()，其中参数是绘图.

To get values actually plotted you can use function ggplot_build() where argument is your plot.

p <- ggplot(mtcars,aes(mpg))+geom_histogram()+
      facet_wrap(~cyl)+geom_vline(data=data.frame(x=c(20,30)),aes(xintercept=x))

pg <- ggplot_build(p)

这将创建列表，并且子列表之一被命名为data.此子列表包含具有在绘图中使用的值的数据框，例如，对于直方图，它包含y值(与count相同).如果使用构面，则列PANEL显示使用哪个构面值.如果绘图中有多个geom_，则数据将包含每个数据帧-在我的示例中，直方图有一个数据框，而vlines有一个数据框.

This will make list and one of sublists is named data. This sublist contains dataframe with values used in plot, for example, for histrogramm it contains y values (the same as count). If you use facets then column PANEL shows in which facet values are used. If there are more than one geom_ in your plot then data will contains dataframes for each - in my example there is one dataframe for histogramm and another for vlines.

head(pg$data[[1]])
  y count         x ndensity ncount density PANEL group ymin ymax
1 0     0  9.791667        0      0       0     1     1    0    0
2 0     0 10.575000        0      0       0     1     1    0    0
3 0     0 11.358333        0      0       0     1     1    0    0
4 0     0 12.141667        0      0       0     1     1    0    0
5 0     0 12.925000        0      0       0     1     1    0    0
6 0     0 13.708333        0      0       0     1     1    0    0
      xmin     xmax
1  9.40000 10.18333
2 10.18333 10.96667
3 10.96667 11.75000
4 11.75000 12.53333
5 12.53333 13.31667
6 13.31667 14.10000

head(pg$data[[2]])
  xintercept PANEL group xend  x
1         20     1     1   20 20
2         30     1     1   30 30
3         20     2     2   20 20
4         30     2     2   30 30
5         20     3     3   20 20
6         30     3     3   30 30

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