R编程：plyr如何使用ddply计算列中的值[重复]

Question

我想将我的数据的通过/失败状态总结如下。换句话说，我想告诉每个产品/类型的通过和失败案例的数量。

library(ggplot2)
library(plyr)
product=c("p1","p1","p1","p1","p1","p1","p1","p1","p1","p1","p1","p1","p2","p2","p2","p2","p2","p2","p2","p2","p2","p2","p2","p2")
type=c("t1","t1","t1","t1","t1","t1","t2","t2","t2","t2","t2","t2","t1","t1","t1","t1","t1","t1","t2","t2","t2","t2","t2","t2")
skew=c("s1","s1","s1","s2","s2","s2","s1","s1","s1","s2","s2","s2","s1","s1","s1","s2","s2","s2","s1","s1","s1","s2","s2","s2")
color=c("c1","c2","c3","c1","c2","c3","c1","c2","c3","c1","c2","c3","c1","c2","c3","c1","c2","c3","c1","c2","c3","c1","c2","c3")
result=c("pass","pass","fail","pass","pass","pass","fail","pass","fail","pass","fail","pass","fail","pass","fail","pass","pass","pass","pass","fail","fail","pass","pass","fail")
df = data.frame(product, type, skew, color, result)

以下 cmd 返回通过+失败案例的总数，但我想要单独的列用于通过和失败

dfSummary <- ddply(df, c("product", "type"), summarise, N=length(result))

结果是：

        product type N
 1      p1      t1   6
 2      p1      t2   6
 3      p2      t1   6
 4      p2      t2   6

理想的结果是

         product type Pass Fail
 1       p1      t1   5    1
 2       p1      t2   3    3
 3       p2      t1   4    2
 4       p2      t2   3    3

我尝试过类似的事情：

 dfSummary <- ddply(df, c("product", "type"), summarise, Pass=length(df$product[df$result=="pass"]), Fail=length(df$product[df$result=="fail"]) )

但显然这是错误的，因为结果是失败和通过的总和。

提前感谢您的建议！ 问候， 里亚德。

Answer 1

您也可以使用reshape2::dcast。

library(reshape2)
dcast(product + type~result,data=df, fun.aggregate= length,value.var = 'result')
##   product type fail pass
## 1      p1   t1    1    5
## 2      p1   t2    3    3
## 3      p2   t1    2    4
## 4      p2   t2    3    3

Answer 2

试试：

dfSummary <- ddply(df, c("product", "type"), summarise, 
                   Pass=sum(result=="pass"), Fail=sum(result=="fail") )

这给了我结果：

  product type Pass Fail
1      p1   t1    5    1
2      p1   t2    3    3
3      p2   t1    4    2
4      p2   t2    3    3

解释：

1. 您将数据集df 提供给ddply 函数。
2. ddply 正在拆分变量“产品”和“类型”
   • 这会导致 length(unique(product)) * length(unique(type)) 片段（即数据 df 的子集）在两个变量的每个组合上拆分。
3. 对于每个部分，ddply 应用您提供的某些功能。在这种情况下，您计算result=="pass" 和result=="fail" 的数量。
4. 现在ddply 为每个部分留下了一些结果，即您拆分的变量（产品和类型）和您请求的结果（通过和失败）。
5. 它将所有部分组合在一起并返回