我有以下数据框叫做workfile：
head(workfile)
times users signal log
14 2014-01-13 00:00:16 00250902DC7D true ON
28 2014-01-13 00:00:47 00250902DC7D true ON
42 2014-01-13 00:01:18 00250902DC7D true ON
56 2014-01-13 00:01:48 00250902DC7D true ON
70 2014-01-13 00:02:19 00250902DC7D true ON
84 2014-01-13 00:02:50 00250902DC7D true ON
我有14个不同的用户，基本上我想计算每个用户的时差。我正在使用ddply，但它不起作用，我不明白原因
hope<-ddply(workfile,.
.(users),transform,diff=c(difftime(tail(workfile$times,-1),head(workfile$times,-1)), NA))
这是错误信息：
* 属性错误（out）＆lt; - attributes（col）：'names'属性[9]的长度必须与vector [8] * '< / p>
此外，如果我附加了我的数据框并启动了相同的命令，则会出现错误消息更改：
attach(workfile)
hope<-ddply(workfile, .(users), transform, diff = c(difftime(tail(times, -1),head(times,-1)), NA))
* as.POSIXct.POSIXlt（time1）出错：无效'x'参数 *
这也很奇怪......
我注意到，只要用户（在第3列中）相同，就没有任何错误。如果我尝试使用具有不同用户的数据框，就会发生这种情况......显然我的代码在tail(...),head(...)部分不正确我的目标是为所有用户计算时差并明确地计算...
我已将dput与我的数据框样本一起使用：
head(pino)
> pino
times users signal log
319001 2014-01-16 21:57:46 00250902FA92 true ON
319006 2014-01-16 21:57:46 002509030E53 true ON
319007 2014-01-16 21:57:46 002509030C41 true ON
319011 2014-01-16 21:57:46 00250902DC7D true ON
319014 2014-01-16 21:57:49 00250902FB05 true ON
319015 2014-01-16 21:57:49 00250902FA92 true ON
319020 2014-01-16 21:57:49 002509030E53 true ON
319021 2014-01-16 21:57:49 002509030C41 true ON
319025 2014-01-16 21:57:49 00250902DC7D true ON
319028 2014-01-16 21:57:58 00250902FB05 true ON
319029 2014-01-16 21:57:58 00250902FA92 true ON
319034 2014-01-16 21:57:58 002509030E53 true ON
319035 2014-01-16 21:57:58 002509030C41 true ON
319039 2014-01-16 21:57:58 00250902DC7D true ON
319042 2014-01-16 21:58:04 00250902FB05 true ON
319043 2014-01-16 21:58:04 00250902FA92 true ON
> dput(pino)
structure(list(times = structure(list(sec = c(46, 46, 46, 46,
49, 49, 49, 49, 49, 58, 58, 58, 58, 58, 4, 4), min = c(57L, 57L,
57L, 57L, 57L, 57L, 57L, 57L, 57L, 57L, 57L, 57L, 57L, 57L, 58L,
58L), hour = c(21L, 21L, 21L, 21L, 21L, 21L, 21L, 21L, 21L, 21L,
21L, 21L, 21L, 21L, 21L, 21L), mday = c(16L, 16L, 16L, 16L, 16L,
16L, 16L, 16L, 16L, 16L, 16L, 16L, 16L, 16L, 16L, 16L), mon = c(0L,
0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L),
year = c(114L, 114L, 114L, 114L, 114L, 114L, 114L, 114L,
114L, 114L, 114L, 114L, 114L, 114L, 114L, 114L), wday = c(4L,
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L
), yday = c(15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L,
15L, 15L, 15L, 15L, 15L, 15L, 15L), isdst = c(0L, 0L, 0L,
0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L)), .Names = c("sec",
"min", "hour", "mday", "mon", "year", "wday", "yday", "isdst"
), class = c("POSIXlt", "POSIXt")), users = structure(c(3L, 13L,
10L, 1L, 4L, 3L, 13L, 10L, 1L, 4L, 3L, 13L, 10L, 1L, 4L, 3L), .Label = c("00250902DC7D",
"00250902FA91", "00250902FA92", "00250902FB05", "00250902FB2E",
"00250902FE0A", "00250902FE63", "002509030AD2", "002509030B9D",
"002509030C41", "002509030C8D", "002509030CE4", "002509030E53",
"002509030E63"), class = "factor"), signal = structure(c(2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("false",
"true"), class = "factor"), log = structure(c(2L, 2L, 2L, 2L,
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("OFF",
"ON"), class = "factor")), .Names = c("times", "users", "signal",
"log"), row.names = c(319001L, 319006L, 319007L, 319011L, 319014L,
319015L, 319020L, 319021L, 319025L, 319028L, 319029L, 319034L,
319035L, 319039L, 319042L, 319043L), class = "data.frame")
现在我有以下错误消息：
Error in attributes(out) <- attributes(col) :
'names' attribute [9] must be the same length as the vector [3]
你怎么看？
答案 0 :(得分：1)
简而言之，如果您转换时间表示，您的功能将起作用：
# Fails
ddply(pino, .(users), transform, diff = c(difftime(tail(times, -1),head(times,-1)), NA))
# Convert time format
pino$times<-as.POSIXct(pino$times)
# Works as expected
ddply(pino, .(users), transform, diff = c(difftime(tail(times, -1),head(times,-1)), NA))
# times users signal log diff
# 1 2014-01-16 21:57:46 00250902DC7D true ON 3
# 2 2014-01-16 21:57:49 00250902DC7D true ON 9
# 3 2014-01-16 21:57:58 00250902DC7D true ON NA
# 4 2014-01-16 21:57:46 00250902FA92 true ON 3
# 5 2014-01-16 21:57:49 00250902FA92 true ON 9
# 6 2014-01-16 21:57:58 00250902FA92 true ON 6
# 7 2014-01-16 21:58:04 00250902FA92 true ON NA
# 8 2014-01-16 21:57:49 00250902FB05 true ON 9
# 9 2014-01-16 21:57:58 00250902FB05 true ON 6
# 10 2014-01-16 21:58:04 00250902FB05 true ON NA
# 11 2014-01-16 21:57:46 002509030C41 true ON 3
# 12 2014-01-16 21:57:49 002509030C41 true ON 9
# 13 2014-01-16 21:57:58 002509030C41 true ON NA
# 14 2014-01-16 21:57:46 002509030E53 true ON 3
# 15 2014-01-16 21:57:49 002509030E53 true ON 9
# 16 2014-01-16 21:57:58 002509030E53 true ON NA
我不清楚为什么会这样。这是mentioned before in another question，而@hadley刚刚声明您应该在POSIXct中使用POSIXlt而不是data.frame。我不清楚为什么。