CODEWITHSUNDEEP
matlabmatrixnan
Saania
Saania

Reputation: 625

Include rows of NaN in matrix at predetermined row numbers.

Initially, I have

Matrix A= 
[ 1   2   3
  4 255   6
NaN NaN NaN
  7   8   9
 10  11  12
NaN NaN NaN 
10    9  11 ];

I find out the row numbers which are all NaN. 

Row_NaN_MatA = [3 6];

After eliminating these rows, I am left with:

Matrix B1 = 
[ 1   2   3
  4 255   6
  7   8   9
 10  11  12
 10    9  11 ];

After applying a filter, I make the second row of Matrix B = NaN NaN NaN. Therefore 

Matrix B2 = 
[ 1   2   3
NaN NaN NaN 
  7   8   9
 10  11  12
 10   9  11 ];

Now, the question is, after all these processing, I want to get the initial matrix back, but with all the deleted elements as NaN. So the required output I want is:

Output Matrix=
[ 1   2   3
NaN NaN NaN
NaN NaN NaN
  7   8   9
 10  11  12
NaN NaN NaN 
10    9  11 ];

I know the dimensions of output I want (= initial Matrix A dimensions), and the row numbers which should be NaN (= Row_NaN_MatA) . The rest of the rows should be equal to rows of Matrix B2.

How can I do this?

Upvotes: 2

Views: 64

Answers (1)

Divakar
Divakar

Reputation: 221504

Use setdiff to get the row IDs that were not part of Row_NaN_MatA by setdiff-ing Row_NaN_MatA with the a 1D array of indices for the entire row extent of A, like so -

output = A
output(setdiff(1:size(A,1),Row_NaN_MatA),:) = B2

You can also use ismember for the same effect -

output(~ismember(1:size(A,1),Row_NaN_MatA),:) = B2

Or use bsxfun there -

output(all(bsxfun(@ne,Row_NaN_MatA(:),1:size(A,1))),:) = B2

Sample run -

>> A
A =
     1     2     3
     4   255     6
   NaN   NaN   NaN
     7     8     9
    10    11    12
   NaN   NaN   NaN
    10     9    11
>> B1
B1 =
     1     2     3
     4   255     6
     7     8     9
    10    11    12
    10     9    11
>> B2
B2 =
     1     2     3
   NaN   NaN   NaN
     7     8     9
    10    11    12
    10     9    11
>> output
output =
     1     2     3
   NaN   NaN   NaN
   NaN   NaN   NaN
     7     8     9
    10    11    12
   NaN   NaN   NaN
    10     9    11

Upvotes: 3

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