使用ddply总结我已经定义了“平均”的功能，并用它在ddply我R中

Question

数据：

average <- function (parameter,speed) { 
    sequence = seq(min(speed), max(speed), by=4.5) 
    interval = cut(speed, sequence) 
    avg = tapply(parameter, interval, mean) 
    avg 
} 


df <- ddply(data1, c(unique('class'),unique('PrecVehClass')), summarise,avg.spacing=average(spacing,velocity),avg.headway=average(headway,velocity),avg.speed=average(velocity,velocity)) 

正如你所看到的，平均函数使用“切割”的时间间隔，然后查找平均。我想在我的输出中显示间隔。目前我得到以下输出：

> head(df) 
    class PrecVehClass avg.spacing avg.headway avg.speed 
1  1   1  129.10  2.50  51.80 
2  1   1  91.80  1.62  56.79 
3  1   2  25.65  6744.06  2.55 
4  1   2  31.86  45.23  7.18 
5  1   2  35.43  3.25  11.63 
6  1   2  38.45  2.85  16.21 

如何添加，其显示的时间间隔的新列（即，最小值和最大值例如[31.8,36.2]）每行中？

编辑

以下是第6排我的数据集：

> dput(head(data1)) 
structure(list(vehicle = c(2L, 2L, 2L, 2L, 2L, 2L), frame = 43:48, 
    globalx = c(6451214.156, 6451216.824, 6451219.616, 6451222.548, 
    6451225.462, 6451228.376), class = c(2L, 2L, 2L, 2L, 2L, 
    2L), velocity = c(37.76, 37.9, 38.05, 38.18, 38.32, 38.44 
    ), acceleration = c(10.44, 9.3, 4.36, -0.73, -1.15, 1.9), 
    lane = c(2L, 2L, 2L, 2L, 2L, 2L), precedingveh = c(0L, 0L, 
    0L, 0L, 0L, 0L), followingveh = c(13L, 13L, 13L, 13L, 13L, 
    13L), spacing = c(0, 0, 0, 0, 0, 0), headway = c(0, 0, 0, 
    0, 0, 0), u = c("no", "no", "no", "no", "no", "no"), PrecVehClass = c(NA_integer_, 
    NA_integer_, NA_integer_, NA_integer_, NA_integer_, NA_integer_ 
    )), .Names = c("vehicle", "frame", "globalx", "class", "velocity", 
"acceleration", "lane", "precedingveh", "followingveh", "spacing", 
"headway", "u", "PrecVehClass"), row.names = c(NA, 6L), class = "data.frame") 

你可以看到我上面定义的平均函数。除了输出中的平均值之外，我还想添加一个显示平均值的“间隔”的新列。如果我不使用ddply但使用tapply的，说avg.spacing，我会得到以下输出：

p <- tapply(data1$spacing, cut(data1$velocity, seq(min(data1$velocity), max(data1$velocity), by=4.5), mean) 

> p 
    (0,4.5] (4.5,9] (9,13.5] (13.5,18] (18,22.5] (22.5,27] (27,31.5] (31.5,36] (36,40.5] (40.5,45] (45,49.5] (49.5,54] 
29.52244 37.44980 44.09410 50.19250 56.89366 61.90450 67.21415 72.83281 79.73360 88.38050 96.87901 105.47172 
(54,58.5] (58.5,63] (63,67.5] (67.5,72] (72,76.5] (76.5,81] (81,85.5] (85.5,90] 
116.13763 120.46700 126.49401 136.43546 174.28593 271.90232 255.20733  NA 

在上面的输出，你可以看到，间隔与间隔的平均值一起报告那个间隔。我想在我的决赛桌这个区间输出是这样的：

> head(df) 
     class PrecVehClass avg.spacing avg.headway avg.speed interval 
    1  1   1  129.10  2.50  51.80 (0,4.5] 
    2  1   1  91.80  1.62  56.79 (4.5,9] 
    3  1   2  25.65  6744.06  2.55 (0,4.5] 
    4  1   2  31.86  45.23  7.18 (4.5,9] 
    5  1   2  35.43  3.25  11.63 (9,13.5] 
    6  1   2  38.45  2.85  16.21 (13.5,18] 

我不知道如何在“平均”功能或ddply命令指定。请帮助

Answer 1

通常，将命令捆绑到一个函数中的一点是，您不必担心中间步骤。你已经做到了，但现在你也需要中间结果（你的“间隔”）。我认为唯一好的解决方案是将你的功能分开。

定义interval首先，你可以使用它作为一个分组变量在ddply，并使用普通的旧mean，除非我误解你的average功能的目的。

df$interval <- with(df, cut(velocity, seq(min(velocity), max(velocity), by = 4.5))) 
df <- ddply(df, c("class", "PrecVehClass", "interval"), summarise, 
      avg.spacing = mean(spacing), 
      avg.headway = mean(headway), 
      avg.speed = mean(velocity)) 

公告同时在ddply分组变量，你不应该需要unique()包装。

---

一个ddply例如：

df1 <- data.frame(x = rnorm(100)) 
df1$interval <- cut(df1$x, breaks=c(-10, -1, 1, 10)) 
ddply(df1, "interval", summarize, mean_within_interval = mean(x)) 
    interval mean_within_interval 
1 (-10,-1]   -1.5262258 
2 (-1,1]   0.0880585 
3 (1,10]   1.4796220