Inserting new element after each element of an array

I have an array arr = [2,4,6]

After converting this array elements to binary using de2bi(arr,'left-msb'), I get

0 1 0

1 0 0

1 1 0

Now what I want to do is to insert 0 after each 0 and 1 after each 1. So the result would be

0 0 1 1 0 0

1 1 0 0 0 0

1 1 1 1 0 0

I tried looping through the array, but since length of binary array is still 3, I can't loop through each element.

Can anyone please help me with this?

Answer 1

[Stephen23]

The MATLAB approach:

arr = [2,4,6];
mat = repelem(de2bi(arr,'left-msb'),1,2)

mat = 3×6

0 0 1 1 0 0 1 1 0 0 0 0 1 1 1 1 0 0

Answer 2

[David Goodmanson]

Hi Neeraj,

not having the communications toolbox I used dec2bin instead, which gives a character array but it is basically the same idea and should work on a binary array I would think.

arr = [2,4,6];
a = dec2bin(arr)
s1 = size(a,1);
s2 = size(a,2);
c(1:s1,1:2:2*s2) = a;
c(1:s1,2:2:2*s2) = a

[Neeraj Chimwal]

that worked. If you don't mind can you please explain me the last two steps

[David Goodmanson]

Hi Neeraj,

The index 1 : 2*s2 is twice as large as the number of columns in 'a'.

In the first step, by using 1:2:2*s2, 'a' is inserted into the odd numbered columns of the new matrix.

In the 2nd step, by using 2:2:2*s2, 'a' is inserted into the even numbered columns of the new matrix.

Answer 3

[DGM]

You should be able to loop through the array regardless of its size. That said, you don't need to.

A=[1 2 3 4];
B=dec2bin(A);

expanded=B(:,round(0.5:0.5:size(B,2)));

which gives:

expanded =
000011
001100
001111
110000

[Neeraj Chimwal]

that worked. Can you please explain the last step? I didn't understand what 0.5:0.5 did here

[DGM]

This bit:

0.5:0.5:size(B,2)

generates a vector like so:

[0.5  1.0  1.5  2.0  2.5  3.0 ... ]

rounding that vector gives us this:

[1  1  2  2  3  3 ... ]

so that we're referencing each element of B twice

Alternatively, you could use something like kron() to generate the same index vector:

kron([1 2 3 4],[1 1])

would yield

[1  1  2  2  3  3  4  4 ]