Inserting an Array into Every Nth Element of Another

Inserting an array into every nth element of another

You can always use a custom Enumerator:

a1 = ['a', 'b', 'c', 'd', 'e', 'f']
a2 = ['g', 'h', 'i']

enum = Enumerator.new do |y|
  e1 = a1.each
  e2 = a2.each
  loop do
    y << e1.next << e1.next << e2.next
  end
end

enum.to_a #=> ["a", "b", "g", "c", "d", "h", "e", "f", "i"]

Or for the general case:

n.times { y << e1.next }

Insert array items into another array eventy nth elements

This should get you on the right track. Note that this modifies the original arrays:

let arr1 = [1,2,3,4,5,6,7,8,9];let arr2 = ['up', 'down', 'left', 'right'];let nth = 2;let result = arr1.reduce((carry, current_value, index, original)=>{    // insert current element of arr1    carry.push(current_value);    // insert from arr2 if on multiple of nth index and there's any left    if((index+1) % nth === 0 && arr2.length!=0){        carry.push(arr2.shift())    }    return carry;}, []);console.log('result', result);

How to insert an element after every other element in python list

Inserting into the middle of a list a bunch of times is going to be very slow for a large dataset. It seems like you can just build a new list like you're doing:

first = [1, 2, 3, 4, 5]
second = []
for i in range(0, len(first) - 1):
    avg = (first[i] + first[i+1]) / 2
    second.append(first[i])
    second.append(avg)
second.append(first[-1])

print(second)

Which prints:

[1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5]

Javascript: insert new member of array after each nth member

Simply change your code to this. Add 3 to itemIndex to account for 1 insertion as well.

var dataRow = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];for (var itemIndex = 2; itemIndex < dataRow.length; itemIndex += 3) {        dataRow.splice(itemIndex, 0, 'insert this');}
console.log(dataRow);

Insert element in Python list after every nth element

I've got two one liners.

Given:

>>> letters = ['a','b','c','d','e','f','g','h','i','j']

1. Use enumerate to get index, add 'x' every 3^rd letter, eg: mod(n, 3) == 2, then concatenate into string and list() it.

   >>> list(''.join(l + 'x' * (n % 3 == 2) for n, l in enumerate(letters)))
   
   ['a', 'b', 'c', 'x', 'd', 'e', 'f', 'x', 'g', 'h', 'i', 'x', 'j']
   

   But as @sancho.s points out this doesn't work if any of the elements have more than one letter.

2. Use nested comprehensions to flatten a list of lists^(a), sliced in groups of 3 with 'x' added if less than 3 from end of list.

   >>> [x for y in (letters[i:i+3] + ['x'] * (i < len(letters) - 2) for
        i in xrange(0, len(letters), 3)) for x in y]
   
   ['a', 'b', 'c', 'x', 'd', 'e', 'f', 'x', 'g', 'h', 'i', 'x', 'j']
   

(a) [item for subgroup in groups for item in subgroup] flattens a jagged list of lists.

Numpy array insert every second element from second array

np.insert would work well:

>>> A = np.array([1, 3, 5, 7])
>>> B = np.array([2, 4, 6, 8])
>>> np.insert(B, np.arange(len(A)), A)
array([1, 2, 3, 4, 5, 6, 7, 8])

However, if you don't rely on sorted values, try this:

>>> A = np.array([5, 3, 1])
>>> B = np.array([1, 2, 3])
>>> C = [ ]
>>> for element in zip(A, B):
        C.extend(element)
>>> C
[5, 1, 3, 2, 1, 3]

Javascript insert element at nth index in array, insertion elements from another array

You can iterate through the smaller array using forEach use splice() to insert elements.

let arr1 = ['1', '2', '3', '4', '5', '6', '7', '8', '9', '10', '11', '12']let arr2 = ['a', 'b', 'c']
function insertArr(arr1,arr2,n){  arr1 = arr1.slice();  arr2.forEach((a,i) => {    arr1.splice(i*n+i,0,a);  })  return arr1;}
console.log(insertArr(arr1,arr2,4))

How to insert a string into a numpy list every nth index?

The second argument for np.insert should be the index to place the values, you can try:

n = 3
np.insert(b, range(n, len(b), n), "\n") 

# array(['a', 'b', 'c', '\n', 'a', 'b', 'c', '\n', 'a', 'b', 'c', '\n', 'a',
#        'b', 'c'], 
#       dtype='<U1')

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