How to Melt single column in R

Question

How to melt single column from T1 to T2.

T1			
Mar-17		T2	
328		Mar-17	328
29.57		Mar-17	29.57
38.483		Mar-17	38.483
31.26		Mar-17	31.26
37.3		Mar-17	37.3
60.026		Mar-17	60.026
47.059		Mar-17	47.059
40.215		Mar-17	40.215
51.79		Mar-17	51.79
45.284		Mar-17	45.284
41.271		Mar-17	41.271
42.411		Mar-17	42.411

and what id I should use to get output in T4 from T3

T3				
Mar-17	Apr-17		T4	
328	396		Mar-17	328
29.57	216.57		Mar-17	29.57
38.483	116.483		Mar-17	38.483
31.26	168.26		Mar-17	31.26
37.3	128.3		Mar-17	37.3
60.026	82.026		Mar-17	60.026
47.059	113.059		Mar-17	47.059
40.215	165.215		Mar-17	40.215
51.79	80.79		Mar-17	51.79
45.284	185.284		Mar-17	45.284
41.271	183.271		Mar-17	41.271
42.411	204.411		Mar-17	42.411
			Apr-17	396
			Apr-17	216.57
			Apr-17	116.483
			Apr-17	168.26
			Apr-17	128.3
			Apr-17	82.026
			Apr-17	113.059
			Apr-17	165.215
			Apr-17	80.79
			Apr-17	185.284
			Apr-17	183.271
			Apr-17	204.411

When I am using stack

T2 <- stack(T1)

it is giving error message

Error in rep.int(names(x), lengths(x)) : invalid 'times' value

Answer 1

I'm able to reproduce your error when I do not have column names (but rather have Mar-17 and Apr-17 as the first observation) so I am assuming that this is how your data is structured. If Mar-17 and Apr-17 are your column names, stack() should work.

In this case, you could set your variable names to be the values in the first row and then use stack() on everything excluding the first row:

names(T1) <- T1[1,]
T2 <- stack(T1[-1, , drop = F])

head(T2)
#       values    ind
#1     328 Mar-17
#2   29.57 Mar-17
#3  38.483 Mar-17
#4   31.26 Mar-17
#5    37.3 Mar-17
#6  60.026 Mar-17

names(T3) <- T3[1,]
T4 <- stack(T3[-1,])

head(T4)
#  values    ind
#1    328 Mar-17
#2  29.57 Mar-17
#3 38.483 Mar-17
#4  31.26 Mar-17
#5   37.3 Mar-17
#6 60.026 Mar-17

---

Data:

T1 <- structure(list(c("Mar-17", "328", "29.57", "38.483", "31.26", 
          "37.3", "60.026", "47.059", "40.215", "51.79", "45.284", "41.271", 
          "42.411")), class = "data.frame", row.names = c(NA, -13L))

T3 <- structure(list(c("Mar-17", "328", "29.57", "38.483", "31.26", 
          "37.3", "60.026", "47.059", "40.215", "51.79", "45.284", "41.271", 
          "42.411"), c("Apr-17", "396", "216.57", "116.483", "168.26", 
          "128.3", "82.026", "113.059", "165.215", "80.79", "185.284", 
          "183.271", "204.411")), row.names = c(NA, -13L), class = "data.frame")