r - 基于整数连接列字符串

Question

例如，我想按首次选举的日期创建如下所示的字符串。

df:

Name         Party       FirstElected
Bob         Liberal      1985
Joe         Republican   1985
Sarah        Green       1980
Bill       Libertarian   1980
Tom       Conservative   1987

目标:

Year            PeopleElected
1985   "Bob (Liberal); Joe (Republican)"
1980   "Sarah (Green); Bill (Libertarian)"
1987   "Tom (Conservative)"

我假设paste和apply/aggregate的某种组合可以做到这一点......但到目前为止我还没有太多运气。

Answer 1

我们可以使用paste/sprintf创建按“FirstElected”分组的格式。我们将“data.frame”转换为“data.table”( setDT(df1) )，按“FirstElected”分组，用括号将“Party”括起来，使用 sprintf 连接“Name” ，然后使用paste ，与 collapse='; '创建单个字符串。

library(data.table)
setDT(df1)[,list(PeopleElected=paste(sprintf('%s (%s)',
                Name, Party), collapse="; ")) , by = FirstElected]
#   FirstElected                     PeopleElected
#1:         1985   Bob (Liberal); Joe (Republican)
#2:         1980 Sarah (Green); Bill (Libertarian)
#3:         1987                Tom (Conservative)

或者使用单个paste

setDT(df1)[, list(PeopleElected=paste(Name, ' (', Party, ')',
           sep='', collapse='; ')) , by=FirstElected]