r - ggplot2 多连续变量绘图

Question

我有一个如下所示的数据集：

  Distance  Mean    SD Median    VI Vegetation.Index       Direction  X X.1 X.2 X.3
1      10m 0.525 0.082  0.530  NDVI             NDVI Whole Landscape NA  NA  NA  NA
2      25m 0.517 0.085  0.523  NDVI             NDVI Whole Landscape NA  NA  NA  NA
3      50m 0.509 0.086  0.514  NDVI             NDVI Whole Landscape NA  NA  NA  NA
4     100m 0.494 0.090  0.497  NDVI             NDVI Whole Landscape NA  NA  NA  NA
5      10m 0.545 0.076  0.551 NDVIe             NDVI            East NA  NA  NA  NA
6      25m 0.542 0.078  0.549 NDVIe             NDVI            East NA  NA  NA  NA


> dput(droplevels(head(data)))
structure(list(Distance = structure(c(2L, 3L, 4L, 1L, 2L, 3L), .Label = c("100m", 
"10m", "25m", "50m"), class = "factor"), Mean = c(0.525, 0.517, 
0.509, 0.494, 0.545, 0.542), SD = c(0.082, 0.085, 0.086, 0.09, 
0.076, 0.078), Median = c(0.53, 0.523, 0.514, 0.497, 0.551, 0.549
), VI = structure(c(1L, 1L, 1L, 1L, 2L, 2L), .Label = c("NDVI", 
"NDVIe"), class = "factor"), Vegetation.Index = structure(c(1L, 
1L, 1L, 1L, 1L, 1L), .Label = "NDVI", class = "factor"), Direction = structure(c(2L, 
2L, 2L, 2L, 1L, 1L), .Label = c("East", "Whole Landscape"), class = "factor"), 
X = c(NA, NA, NA, NA, NA, NA), X.1 = c(NA, NA, NA, NA, NA, 
NA), X.2 = c(NA, NA, NA, NA, NA, NA), X.3 = c(NA, NA, NA, 
NA, NA, NA)), .Names = c("Distance", "Mean", "SD", "Median", 
"VI", "Vegetation.Index", "Direction", "X", "X.1", "X.2", "X.3"
), row.names = c(NA, 6L), class = "data.frame")

我想为每个条形图创建一个条形图分面网格，其中 x 轴上的分类变量（距离）、y 轴上的连续变量（植被指数）和两个条形图（平均和中值植被指数值）。条形图按“方向”和“植被指数”绘制刻面。

我已经用一种类型的度量（平均值）做到了这一点，如下图所示。

这是我现在拥有的代码：

 p = ggplot(data,aes(x=Distance,y=Mean,fill=Distance)) + geom_bar(stat =
    'identity',position='dodge')+ facet_grid(Direction~Vegetation.Index)+ 
    coord_cartesian(ylim=c(0.2,0.95)) + geom_errorbar(data = data,
    aes(ymin=Mean-SD,ymax=Mean+SD),width=0.5)

但我还想要一个中位数栏。

像这样，但对于构​​面网格中的所有条形图。

我发现一些人想要做这个完全相同或类似的事情，并发现它们相当有用：

这个

或这个

但是，我的数据看起来与他们的（我认为）非常不同，并且以任何方式更改它都会弄乱我已经拥有的数据。据我了解，我必须使用 group='Mean+Median'。

Answer 1

使用您的示例数据，我们首先将其转换为长格式。我tidyr::gather在这里使用，但reshape2::melt（或data.table::melt）工作类似。

library(tidyr)
dfl = gather(df, key = measure, value = value, Mean, Median)

dodge_width = 0.8
ggplot(dfl,
       aes(x = measure, y = value, fill = Distance, group = Distance)) +
    geom_bar(stat = 'identity',
             position = position_dodge(dodge_width),
             width = dodge_width) +
    facet_grid(Direction ~ Vegetation.Index) + 
    coord_cartesian(ylim = c(0.2, 0.95)) + 
    geom_errorbar(
        aes(ymin = value - SD, ymax = value + SD),
        width=0.5,
        position = position_dodge(dodge_width)
    )