Convert dataframe into list

Question

I would like to convert a dataframe containing zip codes and relationships between zip codes into a list.

I looked at ways to convert dataframes into lists as well as the spread function.

The first column (codes1) contains all zip codes of a zone. The second column (codes2) contains the zip codes of the cities related to the first one.

df<-as.data.frame(cbind(rep(1:4, c(2,5,4,3)),c(2,4,4,3,6,8,7,1,2,8,7,1,2,3)))
colnames(df)<-c("codes1","codes2")
df

I would like to obtain a list like this one, containing for each zip code the related zip codes:

l <- list(c(2,4), c(4,3,6,8,7),c(1,2,8,7),c(1,2,3))
l

d.b · Accepted Answer · 2019-04-02 15:41:36Z

3

You could just split codes2 by codes1

split(x = df$codes2, f = df$codes1)
#$`1`
#[1] 2 4

#$`2`
#[1] 4 3 6 8 7

#$`3`
#[1] 1 2 8 7

#$`4`
#[1] 1 2 3

You could also loop through unique values of codes1 and select relevant value from codes2

lapply(X = unique(df$codes1),
       FUN = function(x) subset(df$codes2, df$codes1 == x))
#[[1]]
#[1] 2 4

#[[2]]
#[1] 4 3 6 8 7

#[[3]]
#[1] 1 2 8 7

#[[4]]
#[1] 1 2 3

answered Apr 2, 2019 at 15:41

d.b

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