小编mcd*_*fee的帖子

我正在尝试在64位Fedora 21系统上安装Android Studio.

我安装了JRE和JDK先决条件,解压缩了Android Studio安装,并从其"bin"目录下发出"sh studio.sh"来完成安装.

安装向导失败,并显示消息"无法运行mksdcard SDK工具",并建议可能需要32位库.

我想知道在记录的每个出生日期分娩的独特水坝的数量.我的数据框与此类似:

dam <- c("2A11","2A11","2A12","2A12","2A12","4D23","4D23","1X23")
bdate <- c("2009-10-01","2009-10-01","2009-10-01","2009-10-01",
           "2009-10-01","2009-10-03","2009-10-03","2009-10-03")
mydf <- data.frame(dam,bdate)
mydf
#    dam      bdate
# 1 2A11 2009-10-01
# 2 2A11 2009-10-01
# 3 2A12 2009-10-01
# 4 2A12 2009-10-01
# 5 2A12 2009-10-01
# 6 4D23 2009-10-03
# 7 4D23 2009-10-03
# 8 1X23 2009-10-03

我曾经使用aggregate(dam ~ bdate, data=mydf, FUN=length)但它计算了在特定日期生下的所有水坝

bdate dam
1 2009-10-01   5
2 2009-10-03   3

相反,我需要这样的东西:

mydf2
  bdate      dam
1 2009-10-01  2
2 2009-10-03  2

非常感激您的帮忙!