Question

使用以下数据框我想通过复制和分组对数据进行分组，然后计算处理值与控制值的比率。

structure(list(group = structure(c(1L, 1L, 1L, 1L, 2L, 2L, 2L, 
2L), .Label = c("case", "controls"), class = "factor"), treatment = structure(c(1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = "EPA", class = "factor"), 
    replicate = structure(c(2L, 4L, 3L, 1L, 2L, 4L, 3L, 1L), .Label = c("four", 
    "one", "three", "two"), class = "factor"), fatty_acid_family = structure(c(1L, 
    1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = "saturated", class = "factor"), 
    fatty_acid = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = "14:0", class = "factor"), 
    quant = c(6.16, 6.415, 4.02, 4.05, 4.62, 4.435, 3.755, 3.755
    )), .Names = c("group", "treatment", "replicate", "fatty_acid_family", 
"fatty_acid", "quant"), class = "data.frame", row.names = c(NA, 
-8L))

我尝试过如下使用dplyr：

group_by(dataIn, replicate, group) %>% transmute(ratio = quant[group=="case"]/quant[group=="controls"])

但这导致Error: incompatible size (%d), expecting %d (the group size) or 1

最初我认为这可能是因为我试图从df 8行深度创建4个比率，所以我认为summarise可能是答案（将每个组折叠为一个比例）但这不起作用要么（我的理解是一个缺点）。

group_by(dataIn, replicate, group) %>% summarise(ratio = quant[group=="case"]/quant[group=="controls"])

  replicate    group ratio
1      four     case    NA
2      four controls    NA
3       one     case    NA
4       one controls    NA
5     three     case    NA
6     three controls    NA
7       two     case    NA
8       two controls    NA

对于我出错的地方或者使用dplyr可以做到这一点，我会很感激。

感谢。

Answer 1

您可以尝试：

group_by(dataIn, replicate) %>% 
    summarise(ratio = quant[group=="case"]/quant[group=="controls"])
#Source: local data frame [4 x 2]
#
#  replicate    ratio
#1      four 1.078562
#2       one 1.333333
#3     three 1.070573
#4       two 1.446449

由于您按复制和分组进行分组，因此无法同时访问不同组中的数据。

使用dplyr按组计算比率

1 个答案: