这些是我拥有的大型文件的前10行:(请注意，这10行中只有一个用户，但我有成千上万的用户）
dput(testd)
structure(list(user = c(0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L
), otime = structure(c(10L, 9L, 8L, 7L, 6L, 5L, 4L, 3L, 2L, 1L
), .Label = c("2010-10-12T19:56:49Z", "2010-10-13T03:57:23Z",
"2010-10-13T16:41:35Z", "2010-10-13T20:05:43Z", "2010-10-13T23:31:51Z",
"2010-10-14T00:21:47Z", "2010-10-14T18:25:51Z", "2010-10-16T03:48:54Z",
"2010-10-16T06:02:04Z", "2010-10-17T01:48:53Z"), class = "factor"),
lat = c(39.747652, 39.891383, 39.891077, 39.750469, 39.752713,
39.752508, 39.7513, 39.758974, 39.827022, 39.749934),
long = c(-104.99251, -105.070814, -105.068532, -104.999073,
-104.996337, -104.996637, -105.000121, -105.010853,
-105.143191, -105.000017),
locid = structure(c(5L, 4L, 9L, 6L, 1L, 2L, 8L, 3L, 10L, 7L),
.Label = c("2ef143e12038c870038df53e0478cefc",
"424eb3dd143292f9e013efa00486c907", "6f5b96170b7744af3c7577fa35ed0b8f",
"7a0f88982aa015062b95e3b4843f9ca2", "88c46bf20db295831bd2d1718ad7e6f5",
"9848afcc62e500a01cf6fbf24b797732f8963683", "b3d356765cc8a4aa7ac5cd18caafd393",
"d268093afe06bd7d37d91c4d436e0c40d217b20a", "dd7cd3d264c2d063832db506fba8bf79",
"f6f52a75fd80e27e3770cd3a87054f27"), class = "factor"),
dnt = structure(c(10L, 9L, 8L, 7L, 6L, 5L, 4L, 3L, 2L, 1L),
.Label = c("2010-10-12 19:56:49",
"2010-10-13 03:57:23", "2010-10-13 16:41:35", "2010-10-13 20:05:43",
"2010-10-13 23:31:51", "2010-10-14 00:21:47", "2010-10-14 18:25:51",
"2010-10-16 03:48:54", "2010-10-16 06:02:04", "2010-10-17 01:48:53"
), class = "factor"),
x = c(-11674.6344476781, -11683.3414552141,
-11683.0877083915, -11675.3642199817, -11675.0599906624,
-11675.0933491404, -11675.4807522648, -11676.6740962175,
-11691.3894104198, -11675.4691879924),
y = c(4419.73724843345, 4435.719406435, 4435.68538078744,
4420.05048454181, 4420.3000059572, 4420.27721099723,
4420.14288752585, 4420.99619739292, 4428.56278976123,
4419.99099525605),
cellx = structure(c(1L, 2L, 2L, 1L, 1L, 1L, 1L, 1L, 2L, 1L),
.Label = c("[-11682,-11672)", "[-11692,-11682)"
), class = "factor"),
celly = structure(c(1L, 2L, 2L, 1L,
1L, 1L, 1L, 1L, 1L, 1L), .Label = c("[4419,4429)", "[4429,4439)"
), class = "factor"),
cellxy = structure(c(1L, 3L, 3L, 1L,
1L, 1L, 1L, 1L, 2L, 1L), .Label = c("[-11682,-11672)[4419,4429)",
"[-11692,-11682)[4419,4429)", "[-11692,-11682)[4429,4439)"
), class = "factor")), .Names = c("user", "otime", "lat",
"long", "locid", "dnt", "x", "y", "cellx", "celly", "cellxy"), class = "data.frame", row.names = c(NA,
-10L))
关于数据是什么以简化理解的一些解释。 x和y是纬度和长坐标的变换。我已使用cut将x，y位置分离为区间。我希望每个用户获得访问量最大的bin，因此我使用ddply。如下：
cells = ddply(testd, .(user, cellxy), summarise, length(cellxy))
获得：
dput(cells)
structure(list(user = c(0, 0, 0), cellxy = structure(1:3, .Label = c("[-11682,-11672)[4419,4429)",
"[-11692,-11682)[4419,4429)", "[-11692,-11682)[4429,4439)"), class = "factor"),
count = c(7L, 1L, 2L)), .Names = c("user", "cellxy", "count"
), row.names = c(NA, -3L), class = "data.frame")
现在我想要做的是计算每个用户访问最多的bin的第一个数据集的平均x，y，这是从前面的计算中获得的。我不知道如何有效地做到这一点，并且鉴于我的数据集非常大，我会很感激一些指导。谢谢！
答案 0 :(得分：4)
这是两个阶段的方法。首先，修改cells的原始代码 - 对于cellxy和user的每个组合，计算平均x和y值。
cells = ddply(testd, .(user, cellxy), summarise,
cellcount=length(cellxy),meanx=mean(x),meany=mean(y))
cells
user cellxy cellcount meanx meany
1 0 [-11682,-11672)[4419,4429) 7 -11675.40 4420.214
2 0 [-11692,-11682)[4419,4429) 1 -11691.39 4428.563
3 0 [-11692,-11682)[4429,4439) 2 -11683.21 4435.702
然后使用对ddply()的其他来电为最高cellxy的每个用户cellcount进行子集。
cells2 = ddply(cells,.(user),subset,cellcount==max(cellcount))
cells2
user cellxy cellcount meanx meany
1 0 [-11682,-11672)[4419,4429) 7 -11675.4 4420.214
答案 1 :(得分：3)
由于您的数据集很大，您可能需要考虑data.table，它不仅速度快，而且还会使数据更轻松。
library (data.table)
DT <- data.table(testd, by="user")
# Determining which is the most visited, by user
DT[, "MostVisited" := {counts <- table(cellxy); names(counts)[which(counts==max(counts))]}, by=user]
<小时/>
我不确定你想要计算相对于MostVisited的平均x，y的具体程度，但我确信data.table也可以相对直接。
## But perhaps something like this
DT[, c("AvgX", "AvgY") := list(mean(x), mean(y)), by=list(user, MostVisited)]