是否可以仅为分裂变量的某些值返回ddply结果？例如，使用数据框example：
example <- structure(list(shape = structure(c(1L, 1L, 1L, 1L, 2L, 2L, 2L,
2L, 2L, 3L, 3L, 3L, 3L, 3L), .Label = c("circle", "square", "triangle"
), class = "factor"), property = structure(c(1L, 3L, 2L, 1L,
2L, 3L, 1L, 1L, 1L, 1L, 2L, 3L, 1L, 1L), .Label = c("color",
"intensity", "size"), class = "factor"), value = structure(c(5L,
2L, 1L, 5L, 4L, 1L, 5L, 6L, 6L, 7L, 4L, 3L, 6L, 5L), .Label = c("3",
"5", "6", "7", "blue", "green", "red"), class = "factor")), .Names = c("shape",
"property", "value"), class = "data.frame", row.names = c(NA,
-14L))
看起来像这样
shape property value
1 circle color blue
2 circle size 5
3 circle intensity 3
4 circle color blue
5 square intensity 7
6 square size 3
7 square color blue
8 square color green
9 square color green
10 triangle color red
11 triangle intensity 7
12 triangle size 6
13 triangle color green
14 triangle color blue
我想返回一个数据框，其中包含每种具有特定颜色的形状的数量，如下所示：
shape property blue green red
1 circle color 2 0 0
2 square color 1 2 0
3 triangle color 1 1 1
然而，我似乎无法让这个正确归还！我已经使用了类似的东西：
ColorSummary <- ddply(example,.(shape,property="color"), function(example) summary(example$value))
但是这会返回一个数据框，其中包含所有其他唯一value的列（来自属性size和intensity，我不想要）：
shape property 3 5 6 7 blue green red
1 circle color 1 1 0 0 2 0 0
2 square NA 1 0 0 1 1 2 0
3 triangle NA 0 0 1 1 1 1 1
我做错了什么 - 是否有办法返回数据框，就像我展示的第一个结果一样？
此外，虽然这是一个小而快的例子，但我的“真实”数据要大得多，需要很长时间才能计算出来。仅通过限制property="color"来改善ddply的速度吗？
编辑：感谢您的回答！不幸的是，我过度简化了情况，我不确定dcast解决方案是否对我有用。让我解释一下 - 我实际上正在使用数据框example2：
example2 <- structure(list(factory = structure(c(1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L), .Label = c("A",
"B"), class = "factor"), shape = structure(c(1L, 1L, 1L, 1L,
2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 1L, 1L, 1L), .Label = c("circle",
"square", "triangle"), class = "factor"), property = structure(c(1L,
3L, 2L, 1L, 2L, 3L, 1L, 1L, 1L, 1L, 2L, 3L, 1L, 1L, 1L, 3L, 2L
), .Label = c("color", "intensity", "size"), class = "factor"),
value = structure(c(5L, 2L, 1L, 5L, 4L, 1L, 5L, 6L, 6L, 7L,
4L, 3L, 6L, 5L, 5L, 2L, 1L), .Label = c("3", "5", "6", "7",
"blue", "green", "red"), class = "factor")), .Names = c("factory",
"shape", "property", "value"), class = "data.frame", row.names = c(NA,
-17L))
我试图按factory和shape进行拆分。我使用ddply：
ColorSummary2 <- ddply(example2,.(factory,shape,property="color"), function(example2) summary(example2$value))
给出了
factory shape property 3 5 6 7 blue green red
1 A circle color 1 1 0 0 2 0 0
2 A square NA 1 0 0 1 1 2 0
3 A triangle NA 0 0 1 1 1 1 1
4 B circle NA 1 1 0 0 1 0 0
但是我想要返回的是（对于凌乱的表格，我在这里格式化表格时遇到了麻烦）：
factory shape property blue green red
1 A circle color 2 0 0
2 A square NA 1 2 0
3 A triangle NA 1 1 1
4 B circle NA 1 0 0
这可能吗？
编辑2：对于所有的编辑都抱歉，我过分简化了我的情况。这是一个更复杂的数据框，更接近我的真实例子。这个列有一个state列，我不想用它来进行拆分。我可以用ddply做这个（乱七八糟），但是我可以使用dcast忽略state吗？
example3 <- structure(list(state = structure(c(1L, 2L, 1L, 2L, 1L, 2L, 1L,
2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L), .Label = c("CA", "FL"
), class = "factor"), factory = structure(c(1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L), .Label = c("A",
"B"), class = "factor"), shape = structure(c(1L, 1L, 1L, 1L,
2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 1L, 1L, 1L), .Label = c("circle",
"square", "triangle"), class = "factor"), property = structure(c(1L,
3L, 2L, 1L, 2L, 3L, 1L, 1L, 1L, 1L, 2L, 3L, 1L, 1L, 1L, 3L, 2L
), .Label = c("color", "intensity", "size"), class = "factor"),
value = structure(c(5L, 2L, 1L, 5L, 4L, 1L, 5L, 6L, 6L, 7L,
4L, 3L, 6L, 5L, 5L, 2L, 1L), .Label = c("3", "5", "6", "7",
"blue", "green", "red"), class = "factor")), .Names = c("state",
"factory", "shape", "property", "value"), class = "data.frame", row.names = c(NA,
-17L))
答案 0 :(得分：4)
使用dcast中的reshape2：
dcast(...~value,data=subset(example,property=='color'))
Aggregation function missing: defaulting to length
shape property blue green red
1 circle color 2 0 0
2 square color 1 2 0
3 triangle color 1 1 1
使用第二个数据集示例：
dcast(...~value,data=subset(example2,property=='color'))
Aggregation function missing: defaulting to length
factory shape property blue green red
1 A circle color 2 0 0
2 A square color 1 2 0
3 A triangle color 1 1 1
4 B circle color 1 0 0