how can I make the matrix empty when it has the values.

Question

Z D 2017-9-18

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https://ww2.mathworks.cn/matlabcentral/answers/357131-how-can-i-make-the-matrix-empty-when-it-has-the-values

回答： Walter Roberson 2017-9-18

this is my code.

 if  j~= p(t,1)
               D{j}(i,[1,2,3,4])=Cl(i,[1,2,3,4]);
           else 
               Cl(i,[1,2,3,4])% here is my problem I want C1 to be empty but I do not know how to write?!
            end

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Answer 1

Walter Roberson 2017-9-18

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You can delete values, and you can overwrite an entire matrix with an empty matrix, but you cannot overwrite part of a matrix with emptiness, unless the matrix is a cell array.

Cl(i,:) = [];

would delete all of row #i from C1.

c1(i,1) = [];

would delete just the element in column 1 of row #i. But as a side effect, because holes are not allowed in numeric arrays, the entire array would become a single column vector, the same as if you had done:

t = c1(:);                            %make it a column vector
t( sub2ind(size(c1), i, 1) ) = [];    %delete the one element of the column vector
c1 = t;                               %that is the new c1

After that, there would be no c1(i,2) because it would be down to a single column.