cbind in for loop with unequal number of rows - r

Question

This is my data frame
>head(dat)
Var1 Freq
1 89 2
2 95 2
3 97 1
4 99 2
5 103 2
6 104 2
I want to iterate over for loop and append dat$freq using cbind. Is it possible to append the Freq to the same Var1, when NA occurs in Freq?

Answer 1

I think OP is looking to merge a list of data.frames instead of cbind
Following should do the trick.
DF.LIST <- lapply(1:5, function(x) {
rows <- sample(1:5, 1)
data.frame(Var1 = sample(1:5, rows), Freq = sample(5:10, rows))
})
DF.LIST
## [[1]]
## Var1 Freq
## 1 2 6
## 2 4 7
## 3 3 9
## 4 5 10
##
## [[2]]
## Var1 Freq
## 1 3 10
## 2 2 9
##
## [[3]]
## Var1 Freq
## 1 4 5
## 2 3 6
##
## [[4]]
## Var1 Freq
## 1 1 6
## 2 2 10
## 3 5 7
## 4 3 9
## 5 4 8
##
## [[5]]
## Var1 Freq
## 1 5 10
##
OPTION 1
Problem with Reduce & merge combo if used directly on such a list is that it will just end up merging with both Var1 and Freq columns. To avoid that we first rename the second column in each data.frame by adding a index number. After that Reduce and merge combo should give what OP wants.
for (i in 1:length(DF.LIST)) {
names(DF.LIST[[i]]) <- c("Var1", paste0("Freq", i))
}
Reduce(function(...) merge(..., all = T), DF.LIST)
## Var1 Freq1 Freq2 Freq3 Freq4 Freq5
## 1 1 NA NA NA 6 NA
## 2 2 6 9 NA 10 NA
## 3 3 9 10 6 9 NA
## 4 4 7 NA 5 8 NA
## 5 5 10 NA NA 7 10
OPTION 2
You can try following on original DF.LIST directly, but you still need to take care of the column names in the result then.
Reduce(function(...) merge(..., by = "Var1", all = T), DF.LIST)
## Var1 Freq.x Freq.y Freq.x Freq.y Freq
## 1 1 NA 6 NA 9 NA
## 2 2 7 NA NA 8 NA
## 3 3 NA 5 NA 7 7
## 4 4 NA 7 5 5 10
## 5 5 9 9 7 6 NA
Warning messages:
1: In merge.data.frame(..., by = "Var1", all = T) :
column names ‘Freq.x’, ‘Freq.y’ are duplicated in the result
2: In merge.data.frame(..., by = "Var1", all = T) :
column names ‘Freq.x’, ‘Freq.y’ are duplicated in the result