Question

假设我有一个如下所示的数据框（df）：

Patient   VisitDate    Test
   1        1mth       A
   1        2mth       A
   1        3mth       A
   1        4mth       A
   2        1mth       B
   2        2mth       B
   2        3mth       B
   2        4mth       B
   3        1mth       A
   3        2mth       A
   3        3mth       B
   3        4mth       A

以下是制作示例数据框的代码：

df <- data.frame(Patient=c(1,1,1,1,2,2,2,2,3,3,3,3), 
        VisitDate=c("1mth","2mth","3mth","4mth","1mth","2mth","3mth","4mth","1mth","2mth","3mth","4mth"), 
              Test=c("A","A","A","A","B","B","B","B","A","A","B","A"))

我想创建一份包含不同测试的所有患者的列表以及访问日期。如何进行此检查？

是否存在类似＆＃34;由群组申请＆＃34;功能

因此，这个例子的结果将是3号患者3 （因为他参加了测试B和其他测试，其他时间点是测试A）

Answer 1

一些不同的选择：

ave：

df[as.logical(ave(as.character(df$Test),df$Patient,FUN=function(x) x != x[1] )),]

#   Patient VisitDate Test
#11       3      3mth    B

by：

do.call(rbind, by(df, df$Patient, function(x) x[x$Test != x$Test[1],] ))
#  Patient VisitDate Test
#3       3      3mth    B

data.table的{{1}}：

by

在R中按组声明申请？

1 个答案: