Ruby Remove several Elements from array

Question

I have an array filled with several dates

 arry = ["06-01-2014", "07-04-2014", "14-01-2014"
         "14-04-2014", "16-01-2014" "27-03-2014",
         "30-12-2013", "31-03-2014", "27-02-2014"]

I would like to remove element 6 and up Preferably have 2 different arrays.

Is that possible?

arry[5..-1] works great. thanks add it as an answer so I can give you credit. — T0nylombardi
– T0nylombardi, Commented Apr 24, 2014 at 19:10
Please add two commas to arry. No reply req'd, as I'll delete this after you've done the edit. You should always run the code you post to make sure it's working. — Cary Swoveland
– Cary Swoveland, Commented Apr 24, 2014 at 19:59

engineersmnky · Accepted Answer · 2014-04-24 19:30:30Z

Feel free to accept @JanDvorak's answer but you could do this as well

arry = ["06-01-2014", "07-04-2014", "14-01-2014","14-04-2014", "16-01-2014", "27-03-2014","30-12-2013", "31-03-2014", "27-02-2014"]
first_five = arry.shift(5)
#=> ["06-01-2014", "07-04-2014", "14-01-2014", "14-04-2014", "16-01-2014"]
arry 
#=> ["27-03-2014","30-12-2013", "31-03-2014", "27-02-2014"]

or non-destructively (maintaining arry)

arry = ["06-01-2014", "07-04-2014", "14-01-2014","14-04-2014", "16-01-2014", "27-03-2014","30-12-2013", "31-03-2014", "27-02-2014"]
first_five,rest = arry.partition.with_index{|a,i| i < 5}
first_five
#=> ["06-01-2014", "07-04-2014", "14-01-2014", "14-04-2014", "16-01-2014"]
rest
#=> ["27-03-2014","30-12-2013", "31-03-2014", "27-02-2014"]
arry
#=> ["06-01-2014", "07-04-2014", "14-01-2014", "14-04-2014", "16-01-2014","27-03-2014", "30-12-2013", "31-03-2014", "27-02-2014"]

the Tin Man · Accepted Answer · 2014-04-24 21:06:29Z

1

Another way is to delete using index

arry.delete_at(5)

and as @Jan Dvorak mentioned you can split them based on index positions using

arry[0..5] and arry[5..-1]

edited Apr 24, 2014 at 21:06

the Tin Man

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answered Apr 24, 2014 at 19:24

user944938

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2 Comments

Cary Swoveland Over a year ago

What's the point of deleting before slicing? All it does is change arry, which may not be desired.

engineersmnky Over a year ago

delete_at(index) will remove a single element at that index you could use delete_if.with_index and choose what indexes to delete in a block

Cary Swoveland · Accepted Answer · 2014-04-24 21:51:02Z

0

Here's another (non-destructive) way, but nothing could be simpler and clearer than what @Jan suggested.

arr = ["06-01-2014", "07-04-2014", "14-01-2014",
       "14-04-2014", "16-01-2014", "27-03-2014",
       "30-12-2013", "31-03-2014", "27-02-2014"]

[arr.first(5), arr.drop(5)]
  #=> [["06-01-2014", "07-04-2014", "14-01-2014", "14-04-2014", "16-01-2014"],
  #    ["27-03-2014", "30-12-2013", "31-03-2014", "27-02-2014"]]

edited Apr 24, 2014 at 21:51

answered Apr 24, 2014 at 19:51

Cary Swoveland

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3 Comments

engineersmnky Over a year ago

not that it matters I just think it looks reads nicer to use take instead of first when used with drop also it should be [arr.first(5),arr.drop(5)] otherwise you are losing an element.

Cary Swoveland Over a year ago

@engineersmnky, thanks for the correction. (I had misread the question as, in effect, partition on the 6th element.) As for take instead of first, I'm indifferent. You could argue that the word take suggests remove (but we could say the same about drop), whereas first does not.

engineersmnky Over a year ago

I agree but the same argument could be made for drop either way I love to see how many ways you can skin a cat in ruby :)

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