ggplot2排序绘图第二部分

我有一个融化的数据框,dput(x),如下:

## dput(x)    
x <- structure(list(variable = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 
2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 4L, 4L, 4L, 4L, 
4L, 4L), .Label = c("a", "b", "c", "d"), class = "factor"), 
value = structure(c(1L, 
2L, 3L, 4L, 5L, 6L, 1L, 2L, 3L, 4L, 5L, 6L, 1L, 2L, 3L, 4L, 5L, 
6L, 1L, 2L, 3L, 4L, 5L, 6L), .Label = c("Never Heard of", 
"Heard of but Not at all Familiar", 
"Somewhat Familiar", "Familiar", "Very Familiar", "Extremely Familiar"
), class = "factor"), freq = c(10L, 24L, 32L, 90L, 97L, 69L, 
15L, 57L, 79L, 94L, 58L, 19L, 11L, 17L, 34L, 81L, 94L, 85L, 4L, 
28L, 59L, 114L, 82L, 35L)), .Names = c("variable", "value", "freq"
), row.names = c(NA, -24L), class = "data.frame")

看起来是这样的(对于那些不需要测试集的人):

   variable                            value freq
1         a                   Never Heard of   10
2         a Heard of but Not at all Familiar   24
3         a                Somewhat Familiar   32
4         a                         Familiar   90
5         a                    Very Familiar   97
6         a               Extremely Familiar   69
7         b                   Never Heard of   15
8         b Heard of but Not at all Familiar   57
9         b                Somewhat Familiar   79
10        b                         Familiar   94
11        b                    Very Familiar   58
12        b               Extremely Familiar   19
13        c                   Never Heard of   11
14        c Heard of but Not at all Familiar   17
15        c                Somewhat Familiar   34
16        c                         Familiar   81
17        c                    Very Familiar   94
18        c               Extremely Familiar   85
19        d                   Never Heard of    4
20        d Heard of but Not at all Familiar   28
21        d                Somewhat Familiar   59
22        d                         Familiar  114
23        d                    Very Familiar   82
24        d               Extremely Familiar   35

ggplot(x, aes(variable, freq, fill = value)) + 
geom_bar(position = "fill") + 
coord_flip() + 
scale_y_continuous("", formatter="percent")

我想做的是排序a,b,c,d由最高到最低的“频率”的“非常熟悉”

?relevel 和 ?reorder 没有提供任何关于这个用法的建设性例子。

谢谢你的帮助。

贝布