How to Group a Vector into a List of Vectors

How to group a vector into a list of vectors?

split.data.frame is a good way to organize this; then extract the color component.

d <- data.frame(dressId=c(6,9,10,10,10,12,12),
               color=factor(c("yellow","red","green",
                              "purple","yellow",
                              "purple","red"),
                 levels=c("red","orange","yellow",
                          "green","blue","purple")))

I think the version you want is actually this:

ss <- split.data.frame(d,d$dressId)

You can get something more like the list you requested by extracting the color component:

lapply(ss,"[[","color")

Function to group elements of a vector/list

split can separate a vector into lists (among other things) based on factors. See ?split for more information. I became interested in grouping vector of words based on anagrams. So here's one solution for that

vec = c("stop", "pots", "leaves")
split(vec, sapply(vec, function(x)
    paste(sort(unlist(strsplit(tolower(gsub(" ", "", x)), ""))), collapse = "")))
#$aeelsv
#[1] "leaves"

#$opst
#[1] "stop" "pots"

How can I add a vector to a list of vectors in R?

You should use list when with [

e[4] <- list(c(5, 3))

since [ store data in terms of list in your case.

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Or just [[ for assignment

e[[4]] <- c(5,3)

You can type ?[ and read for more information.

R turn each element in a vector into a list of lists

you could use

lapply(vector,list)

Edit: for new desired output

sapply(vector,list)

Split a data.frame by group into a list of vectors rather than a list of data.frames

Using base R only with split. It should be faster than the == with unique

with(df, split(id, group))

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Or with tidyverse we can pull the column after the group_split. The group_split returns a data.frame/tibble and could be slower compared to the split only method above. But, here, we can make some performance improvements by removing the group column (keep = FALSE) and then in the list, pull the 'id' column to create the list of vectors

library(dplyr)
library(purrr)
df %>%
     group_split(group, keep = FALSE) %>% 
     map(~ .x %>%
             pull(id))

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Or use {} with pipe

df %>%
    {split(.$id, .$group)}

Or wrap with with

df %>%
     with(., split(id, group))

Split column into vectors by group R - independent of column order

You may make df$b a named vector using setNames, and then split it into a list:

split(setNames(df$b, df$a), df$id)
# $id1
# a b c d e 
# 1 2 3 4 5 
# 
# $id2
# a b c d e 
# 5 4 3 2 1

How to append vectors to a list group by group

You may use combn(). Loop over number of elements 0:3 sublist should contain (or 1:3 if empty element not wanted). Except the order this is equivalent to Python [[], [1], [1, 2], [1, 2, 10], [1, 10], [2], [2, 10], [10]].

lapply(0:3, \(m) combn(c(1, 2, 10), m, simplify=FALSE)) |>
  unlist(recursive=FALSE) 
# [[1]]
# numeric(0)
# 
# [[2]]
# [1] 1
# 
# [[3]]
# [1] 2
# 
# [[4]]
# [1] 10
# 
# [[5]]
# [1] 1 2
# 
# [[6]]
# [1]  1 10
# 
# [[7]]
# [1]  2 10
# 
# [[8]]
# [1]  1  2 10

Note: R >= 4.1 used.

How do I split a vector into a list of vectors when a condition is met?

The following line seems to work just fine:

split(x,cumsum(x==0))

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