Normalizing CSV columns in Ruby

Question

I've imported a dataset from CSV into Ruby as an array of arrays (each row is an array). I want to normalize each column from 0 to 1. Therefore, I have to find the max and min of each column. Is there an easy way to do this? Or do I have to parse each column value out of each row?

Thanks!

Paul Hoffer · Accepted Answer · 2012-01-18 22:24:06Z

2

You can use Array#transpose to make the inner arrays be the columns, then use Enumerable#min and #max to get your values.

copy = csv_data.transpose
copy.each do |a| #do whatever you need here
  a.min
  a.max
end

or something like this

copy = csv_data.transpose
arr_min = copy.map(&:min) # returns an array of the min values
arr_max = copy.map(&:max) # returns an array of the max values

edited Jan 18, 2012 at 22:24

answered Jan 18, 2012 at 22:18

Paul Hoffer

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1 Comment

Phrogz Over a year ago

Great answer. Note that—if speed is an issue—you might be able to roughly halve the running time by (less elegantly) using a single each iteration to calculate both min and max. (But maybe not, given that min/max are implemented in C.)

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