如何採取矢量內容爲tidyr反引號變量/ dplyr

Question

我有以下的數據幀，在它的作品，因爲我想 與此代碼：

df <- structure(list(celltype = structure(c(1L, 1L, 2L, 2L, 3L, 3L, 
4L, 4L, 5L, 5L, 6L, 6L, 7L, 7L, 8L, 8L, 9L, 9L, 10L, 10L), .Label = c("Bcells", 
"DendriticCells", "Macrophages", "Monocytes", "NKCells", "Neutrophils", 
"StemCells", "StromalCells", "abTcells", "gdTCells"), class = "factor"), 
    sample = c("SP ID control", "SP ID treated", "SP ID control", 
    "SP ID treated", "SP ID control", "SP ID treated", "SP ID control", 
    "SP ID treated", "SP ID control", "SP ID treated", "SP ID control", 
    "SP ID treated", "SP ID control", "SP ID treated", "SP ID control", 
    "SP ID treated", "SP ID control", "SP ID treated", "SP ID control", 
    "SP ID treated"), `mean(score)` = c(0.160953535029424, 0.155743474395545, 
    0.104788051104575, 0.125247035158472, -0.159665650045289, 
    -0.134662049979712, 0.196249441751866, 0.212256889027029, 
    0.0532668251890109, 0.0738264693971133, 0.151828478029596, 
    0.159941552142933, -0.14128323638966, -0.120556640790534, 
    0.196518649474078, 0.185264282171863, 0.0654641151966543, 
    0.0837989059507186, 0.145111577618456, 0.145448549866796)), .Names = c("celltype", 
"sample", "mean(score)"), row.names = c(7L, 8L, 17L, 18L, 27L, 
28L, 37L, 38L, 47L, 48L, 57L, 58L, 67L, 68L, 77L, 78L, 87L, 88L, 
97L, 98L), class = "data.frame") 

library(tidyr) 
library(dplyr) 

df %>% spread(sample, `mean(score)`) %>% 
    mutate(pairwise_division = `SP ID treated`/`SP ID control`) 
df 

##   celltype SP ID control SP ID treated pairwise_division 
## 1   Bcells 0.16095354 0.15574347   0.9676300 
## 2 DendriticCells 0.10478805 0.12524704   1.1952416 
## 3  Macrophages -0.15966565 -0.13466205   0.8434003 
## 4  Monocytes 0.19624944 0.21225689   1.0815668 
## 5   NKCells 0.05326683 0.07382647   1.3859746 
## 6  Neutrophils 0.15182848 0.15994155   1.0534358 
## 7  StemCells -0.14128324 -0.12055664   0.8532976 
## 8 StromalCells 0.19651865 0.18526428   0.9427313 
## 9  abTcells 0.06546412 0.08379891   1.2800739 
## 10  gdTCells 0.14511158 0.14544855   1.0023222 

注意那裏，行

mutate(pairwise_division = `SP ID treated`/`SP ID control`) 

使用字符串的反向引用。

我想要做的是從 列表中取出那些引用的值。我嘗試這樣做：

content <- c("SP ID treated" , "SP ID control")  

df %>% spread(sample, `mean(score)`) %>% 
    mutate(pairwise_division = content[1]/content[2]) 
df 

但它給了我這個錯誤：

Error: non-numeric argument to binary operator 

怎樣做正確的方式？

Answer 1

如果你想玩參數字符串，你必須使用mutate_()而不是mutate()。例如

df %>% spread(sample, `mean(score)`) %>% 
    mutate_(.dots=list(pairwise_division = 
     substitute(a/b, list(
     a=as.name(content[1]), 
     b=as.name(content[2])) 
    ))) 

as.name()將確保您獲得有效的變量名稱。