blocks|key|1570718|text|Array.zip函数对数组进行元素级组合。它不像Python语法那样简洁，但这里有一种方法可以使用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1570719|weights+=+[1,+2,+3]
data+=+[4,+5,+6]
result+=+Array.new
a.zip(b)+{+%7Cx,+y%7C+result+<<+x+*+y+}+#+For+just+the+one+operation

sum+=+0
a.zip(b)+{+%7Cx,+y%7C+sum+%2B=+x+*+y+}+#+For+both+operations|code-block|syntax|javascript|1570720|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

The Array.zip function does an elementwise combination of arrays. It's not quite as clean as the Python syntax, but here's one approach you could use:

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

sum = 0
a.zip(b) { |x, y| sum += x * y } # For both operations
</code></pre>

blocks|key|1570763|text|Ruby有一个map方法(也称为collect方法)，它可以应用于任何Enumerable对象。如果numbers是一个数字数组，则使用下面的代码行：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1570764|numbers.map{%7Cx%7C+x+%2B+5}|code-block|syntax|javascript|1570765|相当于Python中的以下行：|1570766|map(lambda+x:+x+%2B+5,+numbers)|1570767|有关详细信息，请参阅here或here。|1570768|entityMap|0|LINK|mutability|MUTABLE|url|http://www.globalnerdy.com/2008/06/25/enumerating-enumerable-enumerablecollectenumerablemap/|1|http://www.ruby-doc.org/core/classes/Enumerable.html#M001146^0|7|3|G|7|Z|A|1E|7|0|0|0|0|A|4|0|F|4|1|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]|$9|17|A|18|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|19|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1A|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|1B|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1C|8|@]|D|@$9|1D|A|1E|1|1F]|$9|1G|A|1H|1|1I]]|E|$]]|$1|Q|3|-4|5|6|7|1J|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]|Y|$5|T|U|V|E|$W|Z]]]]

Ruby has a <code>map</code> method (a.k.a. the <code>collect</code> method), which can be applied to any <code>Enumerable</code> object. If <code>numbers</code> is an array of numbers, the following line in Ruby:

<pre><code>numbers.map{|x| x + 5}
</code></pre>

is the equivalent of the following line in Python:

<pre><code>map(lambda x: x + 5, numbers)
</code></pre>

For more details, see <a href="http://www.globalnerdy.com/2008/06/25/enumerating-enumerable-enumerablecollectenumerablemap/" rel="nofollow noreferrer" title="Enumerable#collect / Enumerable#map">here</a> or <a href="http://www.ruby-doc.org/core/classes/Enumerable.html#M001146" rel="nofollow noreferrer">here</a>.

blocks|key|1570784|text|在Ruby+1.9中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1570785|weights.zip(data).map{%7Ca,b%7C+a*b}.reduce(:%2B)|code-block|syntax|javascript|1570786|在Ruby+1.8中：|1570787|weights.zip(data).inject(0)+{%7Csum,(w,d)%7C+sum+%2B+w*d+}|1570788|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

In Ruby 1.9:

<pre><code>weights.zip(data).map{|a,b| a*b}.reduce(:+)
</code></pre>

In Ruby 1.8:

<pre><code>weights.zip(data).inject(0) {|sum,(w,d)| sum + w*d }
</code></pre>

blocks|key|1570842|text|@Michiel+de+Mare|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1570843|您的Ruby+1.9示例可以进一步缩短：|1570844|weights.zip(data).map(:*).reduce(:%2B)|code-block|syntax|javascript|1570845|还要注意的是，在Ruby1.8中，如果你需要ActiveSupport+(来自Rails)，你可以使用：|1570846|weights.zip(data).map(&:*).reduce(&:%2B)|1570847|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|S|8|@]|9|@]|A|$G|H]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

@Michiel de Mare

Your Ruby 1.9 example can be shortened a bit further:

<pre><code>weights.zip(data).map(:*).reduce(:+)
</code></pre>

Also note that in Ruby 1.8, if you require ActiveSupport (from Rails) you can use:

<pre><code>weights.zip(data).map(&amp;:*).reduce(&amp;:+)
</code></pre>

blocks|key|1785909|text|映射的替代方案也适用于两个以上的数组：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1785910|def+dot(*arrays)
++arrays.transpose.map+{%7Cvals%7C+yield+vals}
end

dot(weights,data)+{%7Ca,b%7C+a*b}+

#+OR,+if+you+have+a+third+array

dot(weights,data,offsets)+{%7Ca,b,c%7C+(a*b)%2Bc}|code-block|syntax|javascript|1785911|这也可以添加到Array：|1785912|class+Array
++def+dot
++++self.transpose.map{%7Cvals%7C+yield+vals}
++end
end

[weights,data].dot+{%7Ca,b%7C+a*b}

#OR

[weights,data,offsets].dot+{%7Ca,b,c%7C+(a*b)%2Bc}|1785913|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

An alternative for the map that works for more than 2 arrays as well:

<pre><code>def dot(*arrays)
 arrays.transpose.map {|vals| yield vals}
end

dot(weights,data) {|a,b| a*b} 

# OR, if you have a third array

dot(weights,data,offsets) {|a,b,c| (a*b)+c}
</code></pre>

This could also be added to Array:

<pre><code>class Array
 def dot
 self.transpose.map{|vals| yield vals}
 end
end

[weights,data].dot {|a,b| a*b}

#OR

[weights,data,offsets].dot {|a,b,c| (a*b)+c}
</code></pre>

blocks|key|1785935|text|weights+=+[1,2,3]
data++++=+[10,50,30]

require+'matrix'
Vector[*weights].inner_product+Vector[*data]+#+=>+200+|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1785936|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>weights = [1,2,3]
data = [10,50,30]

require 'matrix'
Vector[*weights].inner_product Vector[*data] # =&gt; 200 
</code></pre>

I'm wondering if there's a way to do what I can do below with Python, in Ruby:

<pre><code>sum = reduce(lambda x, y: x + y, map(lambda x, y: x * y, weights, data))
</code></pre>

I have two arrays of equal sizes with the weights and data but I can't seem to find a function similar to map in Ruby, reduce I have working.

Mapping values from two array in Ruby

Python

我想知道是否有一种方法可以用Ruby用Python做下面的事情：sum = reduce(lambda x, y: x + y, map(lambda x, y: x * y, weights, data))我有两个大小相等的数组，权重和数据相同，但我似乎找不到一个类似于Ruby中的map的函数，reduce。

问Ruby中两个数组的映射值
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