insert specific number of rows into matrix if condition is met and fill new cells with specific value

Hi,

I have a 2-column matrix like this:

a = [1 0; 2 0; 4 0; 8 0]

I would like to change this matrix into a matrix like this:

a_new = [1 0; 2 0; 3 NaN; 4 0; 5 NaN; 6 NaN; 7 NaN; 8 0]

i.e. matrix a with consecutive numbers in the first column and an empty cell or NaN in the added second column.

I managed to insert single rows where they should be inserted:

first_column = a(:,1);
d = diff(first_column);
f = find(d>1);
row = [0, NaN];
a = insertrows(a,row,f)

... giving me this:

a =

     1     0
     2     0
     0   NaN
     4     0
     0   NaN
     8     0

But I would need to insert e.g. only one row after row number 3 but three rows after row number 3.

Moreover, I want the new value of the first column to be consecutive number.

I appreciate your help a lot!!

Answer 1

[Andrei Bobrov]

In your case:

n = max(a(:,1));
out = [(1:n)',nan(n,1)];
out(a(:,1),2) = a(:,2);

[Adriana Schatton]

Wow!! This is way more easy than the construction I had in mind!!

Thanks a lot!!

[Andrei Bobrov]

Adriana! Please accept the answer if it helped you.