data.frame rows to a list

user_322912 0
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I have a data.frame which I would like to convert to a list by rows, meaning each row would correspond to its own list elements. In other words, I would like a list that is as long as the data.frame has rows.

So far, I've tackled this problem in the following manner, but I was wondering if there's a better way to approach this.

xy.df <- data.frame(x = runif(10),  y = runif(10))

# pre-allocate a list and fill it with a loop
xy.list <- vector("list", nrow(xy.df))
for (i in 1:nrow(xy.df)) {
    xy.list[[i]] <- xy.df[i,]
}
dataframe r list
12 Answers

A more modern solution uses only purrr::transpose: 

library(purrr)
iris[1:2,] %>% purrr::transpose()
#> [[1]]
#> [[1]]$Sepal.Length
#> [1] 5.1
#> 
#> [[1]]$Sepal.Width
#> [1] 3.5
#> 
#> [[1]]$Petal.Length
#> [1] 1.4
#> 
#> [[1]]$Petal.Width
#> [1] 0.2
#> 
#> [[1]]$Species
#> [1] 1
#> 
#> 
#> [[2]]
#> [[2]]$Sepal.Length
#> [1] 4.9
#> 
#> [[2]]$Sepal.Width
#> [1] 3
#> 
#> [[2]]$Petal.Length
#> [1] 1.4
#> 
#> [[2]]$Petal.Width
#> [1] 0.2
#> 
#> [[2]]$Species
#> [1] 1
user_51696590

A couple of more options :

With asplit

asplit(xy.df, 1)
#[[1]]
#     x      y 
#0.1137 0.6936 

#[[2]]
#     x      y 
#0.6223 0.5450 

#[[3]]
#     x      y 
#0.6093 0.2827 
#....

With split and row

split(xy.df, row(xy.df)[, 1])

#$`1`
#       x      y
#1 0.1137 0.6936

#$`2`
#       x     y
#2 0.6223 0.545

#$`3`
#       x      y
#3 0.6093 0.2827
#....

data

set.seed(1234)
xy.df <- data.frame(x = runif(10),  y = runif(10))
user_39629140

Like @flodel wrote: This converts your dataframe into a list that has the same number of elements as number of rows in dataframe:

NewList <- split(df, f = seq(nrow(df)))

You can additionaly add a function to select only those columns that are not NA in each element of the list:

NewList2 <- lapply(NewList, function(x) x[,!is.na(x)])
user_84989340

Another alternative using library(purrr) (that seems to be a bit quicker on large data.frames)

flatten(by_row(xy.df, ..f = function(x) flatten_chr(x), .labels = FALSE))
user_19188220
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