R iteratively build a dataframe in a loop-CodePudding

I have a loop in R that looks like the following:

    for (i in c(1:10))
{ 
  myvectorlength<-sample(c(1:4),1)
  myvector<-sample(c(1:10),myvectorlength) 
}

I want to build a dataframe with 10 rows that has myvector as the rows. Since myvector can differ in length, I would like to fill any missing values with NA. How would I go about this?

CodePudding user response：

You can use replicate followed by augmenting length to have a constant size, finally convert to dataframe:

myvector <- replicate(10, sample(1:10, sample(1:4)))
myvector <- lapply(myvector, function(x) {
  length(x) <- 4
  x
})
res <- t(as.data.frame(myvector, row.names = 1:4))
rownames(res) <- 1:10
res

   1  2  3  4
1  1 NA NA NA
2  8  3 NA NA
3  3 NA NA NA
4  6 NA NA NA
5  3 10  8 NA
6  7 NA NA NA
7  9  6 NA NA
8  2 NA NA NA
9  8 NA NA NA
10 3  4 NA NA

CodePudding user response：

If you really want to use a for loop:

set.seed(1005) # Set seed for reproducibility

max_col <-  4
n_rows  <- 10
df      <- as.data.frame(matrix(NA_real_, nrow = n_rows, ncol = max_col))
for (i in 1:n_rows) { 
  myvectorlength            <- sample(max_col, 1)
  myvector                  <- sample(10, myvectorlength) 
  df[i, 1:length(myvector)] <- myvector
}

#    V1 V2 V3 V4
# 1   9  2 NA NA
# 2   9  2  5  1
# 3   8  7 NA NA
# 4   8  9  4  3
# 5  10  4  1 NA
# 6   3 NA NA NA
# 7   6 NA NA NA
# 8   2  3 10  4
# 9   9  6 10 NA
# 10  8  4  9 NA

CodePudding user response：

Try this for any different lengths of sample or rows of the data frame

lst <- list()
for (i in c(1:10))
{
  myvectorlength <- sample(c(1:4), 1)
  myvector <- sample(c(1:10), myvectorlength)
  lst[[i]] <- myvector
}

#===================================
m <- max(sapply(lst , length))
ans <- matrix(NA , length(lst) , m)

for (i in 1:length(lst)){
  for(j in 1:m){
    ans[i,j] <- lst[[i]][j]
  }
}

ans <- as.data.frame(ans)
#===================================

ans
#>    V1 V2 V3 V4
#> 1   2 NA NA NA
#> 2   4 NA NA NA
#> 3   1  9  4 NA
#> 4   7  2 NA NA
#> 5   2  5  1  6
#> 6  10 NA NA NA
#> 7   7  2 NA NA
#> 8   6  2  3 NA
#> 9   9 10  1 NA
#> 10  7  1  5 NA

^{Created on 2022-06-08 by the reprex package (v2.0.1)}