R,如何堆叠和保留因子

Question

R问题:如何堆叠两列或更多列数字并保留一个因子

我data.frame喜欢这样的:

patient analyte1value analyte2value analyte3value  
pt1 1 3 5  
pt2 2 6 7  
pt3 9 10 2  
...  

我知道我可以使用stack(select=c(columnnames)),但我失去了耐心因素.

我想出去:

pt1 1 analyte1  
pt1 3 analyte2  
pt1 5 analyte3  
pt2 2 analyte1  
pt2 6 analyte2  
...

(我有一种潜在的怀疑,我需要plyr或类似的......)

谢谢.

Answer 1

一种选择是Hadley的其他套餐之一reshape2:

> require(reshape2)
> dat
  patient analyte1 analyte2 analyte3
1     pt1        1        3        5
2     pt2        2        6        7
3     pt3        9       10        2
> melt(dat, id = "patient")
  patient variable value
1     pt1 analyte1     1
2     pt2 analyte1     2
3     pt3 analyte1     9
4     pt1 analyte2     3
5     pt2 analyte2     6
6     pt3 analyte2    10
7     pt1 analyte3     5
8     pt2 analyte3     7
9     pt3 analyte3     2
> str(melt(dat, id = "patient"))
'data.frame':   9 obs. of  3 variables:
 $ patient : Factor w/ 3 levels "pt1","pt2","pt3": 1 2 3 1 2 3 1 2 3
 $ variable: Factor w/ 3 levels "analyte1","analyte2",..: 1 1 1 2 2 2 3 3 3
 $ value   : int  1 2 9 3 6 10 5 7 2

人们可以使用reshape()基础R 以更加冗长的方式做到这一点:

reshape(dat, direction = "long", sep = "", varying = 2:4,
        times = names(dat)[2:4], idvar = "patient",
        timevar = "variable", v.names = "value")

主要区别在于variable不是基数因素reshape().我认为用户不友好是写作的动机reshape2......