In R program, the list length is unknow.It is generated from for loop. for example:
ls <- list()
ls[[1]] <- 5
ls[[3]] <- a
ls[[6]] <- 8
....
Some index(ordinal number) is undefined.
I want to convert to data frame, such as follows:
1 5
2 NA
3 a
4 NA
5 NA
6 8
...
Additional question: how to get the ordinal number range of this list?
A base R approach could be, assuming here you have "ls" is already there in the environment :
Explanation: We first iterate through all all the elements using lapply, In the anonymous function part, we try to find the null values, where ever there is null value found , we replace with NA. Once the list NULL values are replaced with NA, we bind them row wise using 'rbind' from do.call. To get the last part as sequence, we can use either seq function or colon operator to create a sequence.
dfs <- data.frame(col1 = do.call('rbind', lapply(ls,
function(x)ifelse(is.null(x), NA, x))),
col2 = seq(1,length(ls)), stringsAsFactors = F)
Alternate Using unlist(instead of do.call and rbind) :
dfs <- data.frame(col1 = unlist(lapply(ls,
function(x)ifelse(is.null(x), NA, x))), col2 =
seq(1,length(ls)), stringsAsFactors = F)
Output:
> dfs
# col1 col2
# 1 3 1
# 2 NA 2
# 3 6 3
# 4 NA 4
# 5 NA 5
# 6 8 6
