Comparing values from a multidimentional array using Python

Question

I have an array of numbers:

a=  [[0, 0.1667],
 [1, 0.1667],
 [2, 0.25], 
 [3, 0.25],
 [4, 0.167]].

Each pair contains numbers and their proportions.

I want to compare a particular number Z with the resulted proportions. Lets assume, Z=0.02. So I have to iterate through the proportions and compare each proportion with Z and find the number whose proportion falls below Z and print that number only.

I think, the proportions need to sorted from highest to lowest first and then it has be compared with Z.

adrianus · Accepted Answer · 2015-07-21 06:04:38Z

1

Sorting will be helpful if you're dealing with lots of data, then you can just loop until the first element is bigger than z and you're done.

However, an easy way for going through all elements would be using a list comprehension:

a = [[0, 0.1667],
 [1, 0.1667],
 [2, 0.25], 
 [3, 0.25],
 [4, 0.167]]

z = 0.2
print [x for x in a if x[1] < z]

This will iterate through all elements in a and check if the second number of each element in a is less than z, if yes, they get added to the new list.

Output:

>>> 
[[0, 0.1667], [1, 0.1667], [4, 0.167]]

(I chose z = 0.2, because with z = 0.02 the list is empty :) )

answered Jul 21, 2015 at 6:04

adrianus

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Comments

0xc0de · Accepted Answer · 2015-07-21 06:08:41Z

0

If you have to work with a single such array with multiple values of Z, then sorting will be helpful. Otherwise simply loop over the array and compare proportions with Z and create your desired list. Sorting the array in this case would be more expensive.

PS: If your question is how to sort the array according to proportions:

a.sort(key=lambda x: x[1]))

edited Jul 21, 2015 at 6:08

answered Jul 21, 2015 at 6:01

0xc0de

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