looping in a Data frame-CodePudding

I'm pretty new in R and I would like to know why this operation doesn't allow me to keep looping through a data frame.

I have a dataframe filled with the following data (take note that it only has one column):

1,230.1,37.8,69.2,22.1 <-- this is treated as a column like "1,230.1,37.8,69.2,22.1"
2,44.5,39.3,45.1,10.4
3,17.2,45.9,69.3,9.3
4,151.5,41.3,58.5,18.5
5,180.8,10.8,58.4,12.9

for that I'm creating a empty dataframe as the target:

my.df <- data.frame(matrix(ncol = 5, nrow = 200))
colnames(my.df) <- c('i', 'a', 'b', 'c', 'label')

And I'm trying to parse every string to the target dataframe. But it doesn't fill it completly, just the first row. I believe the problem is with this line temp <- strsplit(a, ",")[[1]] it should only substring one value and keep going, but it stops in the first iteration.

helper <- 1
for(a in DF){
  temp <- strsplit(a, ",")[[1]]
  print(temp)
  my.df[helper, 1] <- temp[1]
  my.df[helper, 2] <- temp[2]
  my.df[helper, 3] <- temp[3]
  my.df[helper, 4] <- temp[4]
  my.df[helper, 5] <- temp[5]
  helper <- helper   1
}

At the end I only have this output:

     i    a    b          c   label
1    1 230.1  37.8      69.2  22.1
2 <NA>  <NA>  <NA>      <NA>  <NA>
3 <NA>  <NA>  <NA>      <NA>  <NA>
4 <NA>  <NA>  <NA>      <NA>  <NA>
5 <NA>  <NA>  <NA>      <NA>  <NA>
6 <NA>  <NA>  <NA>      <NA>  <NA>

Any ideas on how to accomplish this task or explain me why the loop dies in the first iteration? thank you.

CodePudding user response：

Instead of splitting the string, we could directly parse it with read.csv

read.csv(text = DF, header = FALSE, 
     col.names = c('i', 'a', 'b', 'c', 'label'), fill = TRUE)

-output

 i     a    b    c label
1 1 230.1 37.8 69.2  22.1
2 2  44.5 39.3 45.1  10.4
3 3  17.2 45.9 69.3   9.3
4 4 151.5 41.3 58.5  18.5
5 5 180.8 10.8 58.4  12.9

If it is a column in the dataset, extract the column and use read.csv

read.csv(text = DF1$col1, header = FALSE, 
     col.names = c('i', 'a', 'b', 'c', 'label'), fill = TRUE)
  i     a    b    c label
1 1 230.1 37.8 69.2  22.1
2 2  44.5 39.3 45.1  10.4
3 3  17.2 45.9 69.3   9.3
4 4 151.5 41.3 58.5  18.5
5 5 180.8 10.8 58.4  12.9

Regarding the for loop issue, the helper <- helper 1 doesn't have any effect on the iteration. Instead, it can be

for(i in seq_along(DF1[[1]])) my.df[i,] <- strsplit(DF1[[1]][i], ",")[[1]]
> head(my.df)
     i     a    b    c label
1    1 230.1 37.8 69.2 22.1 
2    2  44.5 39.3 45.1  10.4
3    3  17.2 45.9 69.3   9.3
4    4 151.5 41.3 58.5  18.5
5    5 180.8 10.8 58.4  12.9
6 <NA>  <NA> <NA> <NA>  <NA>

data

DF <- "1,230.1,37.8,69.2,22.1 
2,44.5,39.3,45.1,10.4
3,17.2,45.9,69.3,9.3
4,151.5,41.3,58.5,18.5
5,180.8,10.8,58.4,12.9"
DF1 <- structure(list(col1 = c("1,230.1,37.8,69.2,22.1 ", "2,44.5,39.3,45.1,10.4", 
"3,17.2,45.9,69.3,9.3", "4,151.5,41.3,58.5,18.5", "5,180.8,10.8,58.4,12.9"
)), class = "data.frame", row.names = c(NA, -5L))