From: Martin DeMello <martindemello@...>
Date: 2009-02-16T19:57:25+09:00
Subject: Re: How to do this complicated logic in ruby

On Mon, Feb 16, 2009 at 3:30 PM, Valentino Lun <sumwo@yahoo.com> wrote:
> Dear all
>
> I have an array with size around 1000, I want to perform some data
> checking and correction in this array.
>
> For instance, the first record of this array is a hash, as follow
> my_array[0] = {"server"=>"AHN", "hosp"=>"AHN", "loc"=>"PC1",
> "pspec"=>"ANA", "number"=>"1", "pcat"=>"1"}
>
> server  hosp  loc   pspec   pcat
> AHN     AHN   PC1   ANA     1
> PWH     AHN   PC1   ANA     1
> NDH     AHN   PC1   ANA     2     <= This pcat value need update in
> array1
> TMH     AHN   PC1   ANA     2     <= This pcat value need update in
> array1
> .......
> .....
> ...
> (around 1000 records)
>
> When keys hosp, loc, pspec has the same values, their pcat must be
> identical. So, there is problem in the last two records, the key pcat
> should be 1, because the pcat is correct if array["server"] equal to
> array["hosp"].

Simple way:

1. Have a 'signature' for each row, composed of the hosp, loc and
pspec. Could be as simple as

def signature(ary, row)
  %w(hosp loc pspec).map {|k| ary[row][k]}.join(",")
end

2. Collect all the rows with the same signature

verify = Hash.new {|h,k| h[k] = []}
ary.each_with_index {|row, i|
   h[signature(ary, row)] << [i, row['pcat']]
}

3. See if there are any problems

verify.each_pair {|k, v|
  if v.length > 1
    fix_array_for(v)
  end
}

4. Write fix_array_for(v)

Note that v is an array of pairs of [index, pcat]. So for your
example, it would be
[[0,1], [1,1], [2,2], [3,2]]

you basically need to iterate over that array, see which pcat is
right, then iterate over it once more and set all the pcats to the
right value.

There are probably more efficient ways to do all this, but this has
the advantage of being straightforward.

martin