[英]How do I find the index of the maximum value of an array?
我嘗試了這里推薦的解決方案- 在Ruby中,最干凈的方法是獲取數組中最大值的索引?
array = [nil, nil, nil, nil, nil, 0.9655172413793104, nil, nil]
idx = array.each_with_index.max[1]
但是有一些例外:
ArgumentError: comparison of Array with Array failed
from (irb):4:in `each'
from (irb):4:in `each_with_index'
from (irb):4:in `each'
from (irb):4:in `max'
from (irb):4
from /Users/davea/.rvm/gems/ruby-2.4.0/gems/railties-5.0.3/lib/rails/commands/console.rb:65:in `start'
from /Users/davea/.rvm/gems/ruby-2.4.0/gems/railties-5.0.3/lib/rails/commands/console_helper.rb:9:in `start'
from /Users/davea/.rvm/gems/ruby-2.4.0/gems/railties-5.0.3/lib/rails/commands/commands_tasks.rb:78:in `console'
from /Users/davea/.rvm/gems/ruby-2.4.0/gems/railties-5.0.3/lib/rails/commands/commands_tasks.rb:49:in `run_command!'
from /Users/davea/.rvm/gems/ruby-2.4.0/gems/railties-5.0.3/lib/rails/commands.rb:18:in `<top (required)>'
from bin/rails:4:in `require'
from bin/rails:4:in `<main>'
如果要從結果中省略nil
,則可以使用:
array.index(array.compact.max)
或者,如果您希望將nil
視為零,那么首先將它們轉換為Float
:
array.index(array.map(&:to_f).max)
如果出現平局,則將返回第一個最大值的索引。 您還可以使用Array#rindex
獲得最后一個索引。
def max_idx(array)
mx = array.select { |e| e.kind_of?(Numeric) }.max
mx ? array.each_index.select { |i| array[i] == mx } : nil
end
require 'bigdecimal'
max_idx [nil,3,1] #=> [1]
max_idx [nil,3.2,"cat",1] #=> [1]
max_idx [nil,3,nil,1,3] #=> [1,4]
max_idx [nil,3.2,nil,1,3.2] #=> [1,4]
max_idx [nil,Rational(3),1] #=> [1]
max_idx [nil,BigDecimal.new("3"),1] #=> [1]
max_idx [nil,nil,nil] #=> nil
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