How to select specific elements in a matrix?

Question

Tin Nguyen 2015-10-10

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https://ww2.mathworks.cn/matlabcentral/answers/247874-how-to-select-specific-elements-in-a-matrix

评论： the cyclist 2015-10-11

Say I have a 10x10 matrix

x =

  24     1     8    15
   5     7    14    16
   6    13    20    22
  12    19    21     3
  18    25     2     9

And I want to select a certain element from each row in the matrix for example: I want elements from row 1 column 3, row 2 column 4, row 4 column 3, row 5 column 3 and turn those element into 0. I know I can do something like:

x(1,3)=0;
x(2,4)=0;

etc. But that is time-consuming. Is there a code that I can just write all that in one line? I thought it would be something like:

x=([1 2 3 4], [3 4 3 3])=0;

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Answer 1

the cyclist 2015-10-10

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在 MATLAB Online 中打开

Yes, but you have to use "linear indices":

x = [
    17    24     1     8    15
    23     5     7    14    16
     4     6    13    20    22
    10    12    19    21     3
    11    18    25     2     9]
linearIndices = sub2ind(size(x),[1 2 3 4], [3 4 3 3])
x(linearIndices) = 0

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Tin Nguyen 2015-10-10

Thank you so much! That worked perfectly :) !

the cyclist 2015-10-11

The best form of thanks is accepting a solution that worked for you. (This rewards the person who helped you, and also may help future people with a similar question.)

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