how to skip a cell when output a matrix with varying size to a excel file

I have a matrix that varies its size depending on the user input. I need to output this to a specific column of a excel file(a table) and need to skip a cell after every element of the matrix. so let's say I have

a = [1,2,3,4,5,6,7,8]'

How do I make it

   a = [1,'NaN',2,'NaN',3,'NaN',4,'NaN',5,'NaN',6,'NaN',7,'NaN',8,'NaN']'

Answer 1

[the cyclist]

Here's one way:

a = [1,2,3,4,5,6,7,8]' 
a = [a, nan(size(a))]'
a = a(:)'

Answer 2

[Walter Roberson]

You cannot mix numeric and string in a numeric array.

a_cell = num2cell(a);
a_cell(:,2) = {'NaN'};