bind（）中的顺序是否重要？

Question

我遇到了ggplot绘制两个不同数据集的直方图的问题。

想象一下，我有两张桌子：

histClick = {
id   length
1       4
2       6
3       3
4       2
5       2
6       2
7       2
8       3
9      12
10      2
11      3
12      3
13      3
14      2
15      2
16      4
}

histTest = {
id length
1      3
2      2
3      3
4      4
5      6
6      2
7      4
8      2
}

我在每个表中添加了另一列：

histClick[, "cat"] <- "Click"
histTest[, "cat"] <- "Test"`

这是问题所在。当我想在一个数据框中将这两个表绑定在一起时，看起来顺序变得很重要并影响输出。 ggplot的输出在以下total <- rbind(histTest, histClick)和total <- rbind(histClick, histTest)之间有所不同：

sessions <- as.factor(total$cat)
ggplot(total, aes(total$length, fill = sessions)) + 
    geom_histogram(binwidth = .2) +
    facet_grid(cat ~ ., margins = TRUE, scales = "free") 

total <- rbind(histClick, histTest)：

total <- rbind(histTest, histClick)：

我的问题： 1-为什么我应该以{{1​​}}的方式获得不同的结果？订单有关系吗？

2-如何按照我提供数据的顺序得到正确答案？

任何帮助都会非常感激！

Answer 1

R的回收规则产生了差异。您组合的两个数据帧的长度不同。为了显示差异，我使用了以下两个数据框，唯一的区别是rbind的顺序：

dput(total2)
structure(list(id = structure(c(1L, 9L, 10L, 11L, 12L, 13L, 14L, 
15L, 16L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 1L, 9L, 10L, 11L, 12L, 
13L, 14L, 15L), .Label = c("1", "10", "11", "12", "13", "14", 
"15", "16", "2", "3", "4", "5", "6", "7", "8", "9", "id"), class = "factor"), 
    length = c(4, 5, 3, 2, 2, 2, 2, 3, 1, 2, 3, 3, 3, 2, 2, 4, 
    3, 2, 3, 4, 5, 2, 4, 2), cat = c("Click", "Click", "Click", 
    "Click", "Click", "Click", "Click", "Click", "Click", "Click", 
    "Click", "Click", "Click", "Click", "Click", "Click", "Test", 
    "Test", "Test", "Test", "Test", "Test", "Test", "Test")), .Names = c("id", 
"length", "cat"), row.names = c("2", "3", "4", "5", "6", "7", 
"8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "21", 
"31", "41", "51", "61", "71", "81", "91"), class = "data.frame")

dput(total)
structure(list(id = structure(c(1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 
1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 17L, 10L, 11L, 12L, 13L, 14L, 
15L, 16L), .Label = c("1", "2", "3", "4", "5", "6", "7", "8", 
"id", "10", "11", "12", "13", "14", "15", "16", "9"), class = "factor"), 
    length = c(2, 1, 2, 3, 4, 1, 3, 1, 3, 4, 2, 1, 1, 1, 1, 2, 
    6, 1, 2, 2, 2, 1, 1, 3), cat = c("Test", "Test", "Test", 
    "Test", "Test", "Test", "Test", "Test", "Click", "Click", 
    "Click", "Click", "Click", "Click", "Click", "Click", "Click", 
    "Click", "Click", "Click", "Click", "Click", "Click", "Click"
    )), .Names = c("id", "length", "cat"), row.names = c("2", 
"3", "4", "5", "6", "7", "8", "9", "21", "31", "41", "51", "61", 
"71", "81", "91", "10", "11", "12", "13", "14", "15", "16", "17"
), class = "data.frame")

然后我创建了两个面板图：

sessions <- as.factor(total2$cat)
ggplot(total2, aes(x = id, y = length, fill = cat)) + 
  geom_histogram(stat = "identity") +
  facet_grid(cat ~ ., margins = TRUE, scales = "free")

sessions <- as.factor(total$cat)
ggplot(total, aes(total$length, fill = sessions)) + 
  geom_histogram(binwidth = .2) +
  facet_grid(cat ~ ., margins = TRUE, scales = "free")