我想通过一个因子变量求和一组POSIXct对象,但得到的错误不是为POSIXt对象定义sum
。然而,如果我只是计算平均值,它工作得很好。但是,我怎样才能通过使用tapply的小组得到总结时间?R:使用tapply求和POSIXct对象
实施例:
data <- data.frame(time = c("2:50:04", "1:24:10", "3:10:43", "1:44:26", "2:10:19", "3:01:04"),
group = c("A","A","A","B","B","B"))
data$group <- as.factor(data$group)
data$time <- as.POSIXct(paste("1970-01-01", data$time), format="%Y-%m-%d %H:%M:%S", tz="GMT")
# works
tapply(data$time, data$group, mean)
# doesn't work
tapply(data$time, data$group, sum)
试试'tapply(data $ time,data $ group,function(x)sum(as.nume ric(x)))' –
太棒了,这是我所希望的一种简单的解决方法。只需要转换回h:m:s格式,这非常简单。谢谢! – ageil