Adding rows to matrix based on if-statement in loop

Question

Kai Friedrich 2020-2-5

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https://ww2.mathworks.cn/matlabcentral/answers/503845-adding-rows-to-matrix-based-on-if-statement-in-loop

评论： Star Strider 2020-6-16

Hey,

I have a matrix with numerical values, however, some data is missing and I have to add some additional rows to the matrix.

The problem is that the rows have to added at a specific place of the matrix since the order of the matrix is important.

I would like to automate the process and work with a loop in which rows are added based on an if-statement which refers to specific values in the matrix

The order of the other rows of the matrix should remain the same.

Any ideas how to implement this?

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Stephen23 2020-2-5

编辑：Stephen23 2020-2-5

"Any ideas how to implement this?"

Why do you need a loop?

Preallocate the complete output matrix using nan or zeros, then use indexing to allocate all rows of data in one operation.

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Answer 1

Star Strider 2020-2-5

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/503845-adding-rows-to-matrix-based-on-if-statement-in-loop#answer_413978

在 MATLAB Online 中打开

A = randi(9, 7, 5);                                     % Original Matrix
B = randi([51 59], 2, 5);                               % Rows To Be Inserted
Anew = zeros(size(A,1)+size(B,1), size(A,2));           % Output Matrix Preallocation
NewRows = [3 5];                                        % Define Rowss For Insertion
ARows = setdiff(1:size(Anew,1), NewRows);               % Original Rows In New Matrix
Anew(ARows,:) = A;                                      % Copy Rows
Anew(NewRows,:) = B;                                    % Insert Rows