使用ddply總結我已經定義了「平均」的功能，並用它在ddply我R中

Question

數據：

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，平均函數使用「切割」的時間間隔，然後查找平均。我想在我的輸出中顯示間隔。目前我得到以下輸出：

> 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，其顯示的時間間隔的新列（即，最小值和最大值例如[31.8,36.2]）每行中？

編輯

以下是第6排我的數據集：

> 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義的平均函數。除了輸出中的平均值之外，我還想添加一個顯示平均值的「間隔」的新列。如果我不使用ddply但使用tapply的，說avg.spacing，我會得到以下輸出：

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 

在上面的輸出，你可以看到，間隔與間隔的平均值一起報告那個間隔。我想在我的決賽桌這個區間輸出是這樣的：

> 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。請幫助

Answer 1

通常，將命令捆綁到一個函數中的一點是，您不必擔心中間步驟。你已經做到了，但現在你也需要中間結果（你的「間隔」）。我認爲唯一好的解決方案是將你的功能分開。

定義interval首先，你可以使用它作爲一個分組變量在ddply，並使用普通的舊mean，除非我誤解你的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)) 

公告同時在ddply分組變量，你不應該需要unique()包裝。

---

一個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