creating additonal rows of NaN in specific positions

Dear all,

I have a large matrix (double array of dimension 80000 by 21) and I want to create NaN rows in specific positions.

I have set up a rule [find(gg>300)] according to which I know the positions at which I want to create an additional row that will contain NaNs

For instance, let’s start with a simple example

 A=[

2.4332    4.1477;
  2.6073    4.5900;
  2.2310    3.7442;
  2.4555    4.1178;
  2.5096    4.1946;
  2.7517    4.7802;
  2.8372    4.9423;
  2.9577    5.1563;
  3.2365    5.6061;
  3.0658    5.3787;
  2.9244    5.0497;
  2.6104    4.4623;
  2.5419    4.4164;
  2.4947    4.3577;
  2.5633    4.7050
]

Suppose that the criterion “find” tells me that I have to create additional rows of NaNS in positions 2,4,5,10 Then I want to have

A=[

 2.4332    4.1477;
    2.6073    4.5900;
     NaN      NaN
    2.2310    3.7442;
    2.4555    4.1178;
     NaN      NaN

    2.5096    4.1946;
     NaN      NaN

    2.7517    4.7802;
    2.8372    4.9423;
    2.9577    5.1563;
    3.2365    5.6061;
    3.0658    5.3787;
     NaN      NaN

    2.9244    5.0497;
    2.6104    4.4623;
    2.5419    4.4164;
    2.4947    4.3577;
    2.5633    4.7050
  ]

thanks

Answer 1

[Oleg Komarov]

Very similar to your previous question. You have to build the idx accordingly. Nte that the idx stores the row position where you will allocate A in Anew.

 pos         = [2,4,5,10];
 [r,c]       = size(A);
 add         = numel(pos);            % How much longer Anew is
 Anew        = NaN(r + add,c);        % Preallocate
 idx         = setdiff(1:r+add,pos);  % all positions of Anew except pos
 Anew(idx,:) = A;

[antonet]

thanks Oleg!

[William Garrett]

Hi, I have tried this approach but after the final step I recieve the following error:

'The following error occurred converting from datetime to double: Undefined function 'double' for input arguments of type 'datetime'. To convert from datetimes to numeric, first subtract off a datetime origin, then convert to numeric using the SECONDS, MINUTES, HOURS, DAYS, or YEARS functions'

Are you able to explain to me what I need to do?