# Sorting an array of arrays

I have an array of arrays. The first field of each contained array is a
date. The second field of each contained array is the corresponding day
of the week. I thought that it would be very easy to sort the outer
array on the dates like this:

myArray=[[“2013/09/09”,“Mon”],[“2013/09/14”,“Fri”],[“2013/09/11”,“Wed”]]
myArray.sort {|x,y| x[0] <=> y[0]}
puts(myArray.inspect)

It’s not working for me. Can someone please tell me what I’m missing?
Thanks for any help.

`` ... doug``

ary.sort won’t modify ary in-place.

myArray=[[“2013/09/09”,“Mon”],[“2013/09/14”,“Fri”],[“2013/09/11”,“Wed”]]
sorted = myArray.sort { |x,y| x[0] <=> y[0] }
p sorted

You might also want to check out sort! vs sort.

I think you should try :

myArray=[[“2013/09/09”,“Mon”],[“2013/09/14”,“Fri”],[“2013/09/11”,“Wed”]]
myArray.sort! {|x,y| x[0] <=> y[0]}
puts(myArray.inspect)

notice, sort!

Carlos G

On Sep 22, 2013, at 01:51 PM, Doug J. [email protected] wrote:

I have an array of arrays. The first field of each contained array is a
date. The second field of each contained array is the corresponding day
of the week. I thought that it would be very easy to sort the outer
array on the dates like this:

myArray=[[“2013/09/09”,“Mon”],[“2013/09/14”,“Fri”],[“2013/09/11”,“Wed”]]
myArray.sort {|x,y| x[0] <=> y[0]}
puts(myArray.inspect)

It’s not working for me. Can someone please tell me what I’m missing?
Thanks for any help.

… doug

sort! is definitely the way to go. Thanks so much for the help. (I
should have been able to figure that out.)

``  ... doug``

There’s always sort_by, as well.
myArray.sort_by! { |x| x[0] }

On Sun, Sep 22, 2013 at 8:51 PM, Doug J. [email protected]
wrote:

I have an array of arrays. The first field of each contained array is a
date.

No. It’s a String.

The second field of each contained array is the corresponding day
of the week. I thought that it would be very easy to sort the outer
array on the dates like this:

myArray=[[“2013/09/09”,“Mon”],[“2013/09/14”,“Fri”],[“2013/09/11”,“Wed”]]
myArray.sort {|x,y| x[0] <=> y[0]}
puts(myArray.inspect)

It’s not working for me. Can someone please tell me what I’m missing?
Thanks for any help.

Apart from using sort! you can use sort_by!

irb(main):012:0> a =
[[“2013/09/09”,“Mon”],[“2013/09/14”,“Fri”],[“2013/09/11”,“Wed”]]
=> [[“2013/09/09”, “Mon”], [“2013/09/14”, “Fri”], [“2013/09/11”, “Wed”]]
irb(main):013:0> a.sort_by! {|x| Date.parse(x[0])}
=> [[“2013/09/09”, “Mon”], [“2013/09/11”, “Wed”], [“2013/09/14”, “Fri”]]
irb(main):014:0> a
=> [[“2013/09/09”, “Mon”], [“2013/09/11”, “Wed”], [“2013/09/14”, “Fri”]]

But I’d rather make Date elements part of the Array. Then you have
the proper representation of the data. String is just for input and
output.

Kind regards

robert

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