Mapping values from 2 array in Ruby

I'm asking yourself if there's a means to do what I can do listed below with Python, in Ruby:

sum = reduce(lambda x, y: x + y, map(lambda x, y: x * y, weights, data))

I have 2 selections of equivalent dimensions with the weights and also information yet I can not appear to locate a function comparable to map in Ruby, reduce I have functioning.

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2019-05-09 11:19:03
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Answers: 4

In Ruby 1.9:

weights.zip(data).map{|a,b| a*b}.reduce(:+)

In Ruby 1.8:

weights.zip(data).inject(0) {|sum,(w,d)| sum + w*d }
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2019-05-13 14:45:25
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@Michiel de Mare

Your Ruby 1.9 instance can be reduced a little bit more:

weights.zip(data).map(:*).reduce(:+)

Also keep in mind that in Ruby 1.8, if you call for ActiveSupport (from Rails) you can make use of:

weights.zip(data).map(&:*).reduce(&:+)
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2019-05-13 14:41:48
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Ruby has a map method (a.k.a. the collect method), which can be related to any kind of Enumerable object. If numbers is an array of numbers, the adhering to line in Ruby:

numbers.map{|x| x + 5}

is the matching of the adhering to line in Python:

map(lambda x: x + 5, numbers)

For even more information, see here or here.

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2019-05-12 02:47:35
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The Array.zip function does an elementwise mix of selections. It's not fairly as tidy as the Python syntax, yet below is one strategy you can make use of:

weights = [1, 2, 3]
data = [4, 5, 6]
result = Array.new
a.zip(b) { |x, y| result << x * y } # For just the one operation

sum = 0
a.zip(b) { |x, y| sum += x * y } # For both operations
0
2019-05-12 02:24:38
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