CODEWITHSUNDEEP
r
user3424320
user3424320

Reputation: 43

Extract second element from every item in a list

This additonal information might help. Here is what I am trying to do: This throws more light but here is what I am trying to. Lets say you have a data like the one below –

Region      Open    Store
120..141       +    France
145..2115      +    Germany
3322..5643     +    Wales
5646..7451     -    Scotland
7454..8641     -    Mexico
8655..9860     -    India
9980..11413    +    Zambia
11478..1261    -    Nicaragua
12978..1318    +    Sweeden

What I was trying to do was to pick find the difference between the second element (141) and the consecutive first element (143) and if they meet a certain value and they have the same sign ( + or -), list all their stores together.

Upvotes: 3

Views: 7653

Answers (2)

hrbrmstr
hrbrmstr

Reputation: 78832

I agree with @Dason that understanding the mechanics are important (i.e. you can't treat R like PHP), but if 2.6 hours of fiddling still has you stumped, this might help:

dat <- list(c(100, 150), c(201, 202), c(147, 269), c(301, 401))
second <- sapply(dat, "[", 2) 
first <- sapply(dat[2:length(second)], "[", 1)
second[1:length(first)] - first

Knowing more of what you're really trying to do would help since I'm not fully convinced that's the final result you're looking for.

Upvotes: 3

Dason
Dason

Reputation: 61953

Use sapply and pass to it [ as the function and tell it you want to extract the second element.

# Create your data set
dat <- list(c(100, 150), c(201, 202), c(147, 269), c(301, 401))
dat
#[[1]]
#[1] 100 150
#
#[[2]]
#[1] 201 202
#
#[[3]]
#[1] 147 269
#
#[[4]]
#[1] 301 401
#
sapply(dat, "[", 2)
#[1] 150 202 269 401

Upvotes: 10

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