From: Phrogz <phrogz@...>
Date: 2009-11-22T23:45:55+09:00
Subject: Re: Finding the closest value from a matrix

On Nov 21, 1:04 pm, Mahadev Ittina <mitt...@gmail.com> wrote:
> I have a matrix that looks something like this
>
>        85        90       100       125        150         175
> 8     1.183    1.118     1.006     0.805      0.671      0.575
> 10    1.847    1.744     1.57      1.256      1.047      0.897
> 12    2.659    2.511      ..        ..           ...        ...
> 16    ...       ...        ..     ...           ...        ..
>
> Say, I have a value of 1.1, I want it to automatically choose the
> closest bigger value i.e. 1.118 and say 8 mm diameter at 90 mm spacing.
> How can this be implemented? I thought of creating hashes. but it seems
> too complicated. If anyone is wondering about the formula it goes like
> this.

Create a one-dimensional array where each entry records the value, row
and column number (or row and column headers).

# This should be programmatically done by iterating your array
# not explicitly as I'm showing it here.
Descriptor = Struct.new :row, :col, :value
a = [
  Descriptor.new(0, 0, 1.183),
  Descriptor.new(0, 1, 1.118),
  Descriptor.new(0, 1, 1.006),
  # ..etc.
]

# Sort the array by value
a = a.sort_by{ |desc| desc.value }

# Create a method that finds the closest (larger) value in the array
# via a binary search: http://en.wikipedia.org/wiki/Binary_search
# (Left as an exercise for the reader.)

# Now you know what row and column it came from.