creating additonal rows of NaN in specific positions

Question

antonet 2012-8-7

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/45464-creating-additonal-rows-of-nan-in-specific-positions

评论： William Garrett 2020-2-22

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=[
4332    4.1477;
6073    4.5900;
2310    3.7442;
4555    4.1178;
5096    4.1946;
7517    4.7802;
8372    4.9423;
9577    5.1563;
2365    5.6061;
0658    5.3787;
9244    5.0497;
6104    4.4623;
5419    4.4164;
4947    4.3577;
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=[

4332    4.1477;
6073    4.5900;
     NaN      NaN
2310    3.7442;
4555    4.1178;
     NaN      NaN
5096    4.1946;
     NaN      NaN
7517    4.7802;
8372    4.9423;
9577    5.1563;
2365    5.6061;
0658    5.3787;
     NaN      NaN
9244    5.0497;
6104    4.4623;
5419    4.4164;
4947    4.3577;
5633    4.7050
  ]

thanks

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Answer 1

Oleg Komarov 2012-8-7

2
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/45464-creating-additonal-rows-of-nan-in-specific-positions#answer_55611

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;

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antonet 2012-8-7

thanks Oleg!

William Garrett 2020-2-22

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?

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