tidyr：傳播時不擴展所有列

Question

轉到學習tidyr並遇到spread()問題。

這裏有一個假的實驗數據集：

library(tidyr) 
df <- structure(list(mood = c(0.855, -0.103, 0.421, -0.222, 0.772, -0.027, -1.088, 0.923, -1.516, -1.503, -0.358, -0.357, -0.344, 0.294, 0.348, -0.174, 0.872, -1.188, 0.842, -0.246, -0.758, 0.674, 0.045, 0.72, -1.253, 0.00599999999999995, -0.0749999999999999,1.623, -1.754, -0.44, -0.607, -0.083, -0.827, -0.337, -0.6, 0.429, -0.383, -1.755, 0.894, 0.146, -0.658, -0.409, -0.531, 1.388, -0.688, 0.521, -0.662, 0.852, -1.363, 0.18, -0.775, 0.393, -0.926, 0.809, -0.857, 0.889, 0.0969999999999999, -1.553, -0.21,1.769, -0.114, -0.203, 0.805, 0.186, 0.286, -0.076, 0.137, 1.208, 0.33, 0.34, 0.832, 0.815, -0.427, 0.444, -0.838, 1.45, 1.701, -2.265, 0.531, 0.808), 
    subj = structure(c(1L, 12L, 14L, 15L, 16L, 17L, 18L, 19L, 20L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L,11L, 13L, 1L, 12L, 14L, 15L, 16L, 17L, 18L, 19L, 20L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 13L, 1L, 12L, 14L, 15L, 16L, 17L, 18L, 19L, 20L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 13L, 1L, 12L, 14L, 15L, 16L, 17L, 18L, 19L, 20L, 2L, 3L, 4L, 5L,6L, 7L, 8L, 9L, 10L, 11L, 13L), .Label = c("s1", "s10", "s11", "s12", "s13", "s14", "s15", "s16", "s17", "s18", "s19", "s2", "s20", "s3", "s4", "s5", "s6", "s7", "s8", "s9"), class = "factor"), 
    depressed = structure(c(2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L,1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L,2L, 1L, 2L, 1L, 2L, 1L, 2L, 1L), .Label = c("no", "yes"), class = "factor"), 
    activity = structure(c(2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L,2L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = c("exercize", "relaxation"), class = "factor"), 
    drug = structure(c(1L, 1L,1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L,2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("placebo", "SSRI"), class = "factor")), .Names = c("mood", "subj", "depressed", "activity", "drug"), row.names = c(NA, -80L), class = "data.frame") 

在df採取偷看，我們可以看到，activity和drug是內，主體因素，而depressed是被試間因素：

head(arrange(df, subj)) 
    mood subj depressed activity drug 
1 0.855 s1  yes relaxation placebo 
2 -0.758 s1  yes relaxation SSRI 
3 -0.658 s1  yes exercize placebo 
4 -0.114 s1  yes exercize SSRI 
5 -1.503 s10  no relaxation placebo 
6 -0.440 s10  no relaxation SSRI 

我想將df轉換爲寬屏幕形式，其中每個主題的mood用單獨的列表示，每行對應於activity和drug的組合。不幸的是，我不知道如何避免爲每個級別的depressed創建一組行。這是我到目前爲止有：

df %>% spread(subj, mood) %>% `[`(1:5) 
    depressed activity drug  s1 s10 
1  no exercize placebo  NA 0.18 
2  no exercize SSRI  NA 0.34 
3  no relaxation placebo  NA -1.50 
4  no relaxation SSRI  NA -0.44 
5  yes exercize placebo -0.658 NA 
6  yes exercize SSRI -0.114 NA 
7  yes relaxation placebo 0.855 NA 
8  yes relaxation SSRI -0.758 NA 

我想避免擴大depressed因此產生的輸出將只有四排。

Answer 1

感謝@decendodiscimus在評論中提供解決方案。

以「寬」格式消除主題因素是使用dplyr::select和-的簡單問題。

> library(dplyr) 
> df <- tbl_df(df) 
> df %>% select(-depressed) %>% spread(subj, mood) 
Source: local data frame [4 x 22] 

    activity drug  s1 s10 s11 s12 s13 s14 s15 s16 
1 exercize placebo -0.658 0.180 -0.775 0.393 -0.926 0.809 -0.857 0.889 
2 exercize SSRI -0.114 0.340 0.832 0.815 -0.427 0.444 -0.838 1.450 
3 relaxation placebo 0.855 -1.503 -0.358 -0.357 -0.344 0.294 0.348 -0.174 
4 relaxation SSRI -0.758 -0.440 -0.607 -0.083 -0.827 -0.337 -0.600 0.429