How to find single index values in a matrix?

B1 = [2 4 6 8; 10 12 14 16; 18 20 22 24; 26 28 30 32]
idx_8=find(B1==8)
[row,column]=find(B1~=8)
RowColumn = [row:column]

Find the single index values for 26, 4, and 28?

How is a matrix indexed with single indexing values?

[Walter Roberson]

[was_found, idx] = ismember([26 4 28], B1);

idx will be 0 in places the original was not found.

[Dalton Houghton-Schaffer]

Is that the code to find single index values? And do I insert anything to the matrix [was_found]?

[Walter Roberson]

[was_found, idx] = ismember([26 4 28], B1);

will assign to two variables: was_found and idx. was_found will be true for each element of [26 4 28] that was located somewhere in B1, and will be false for any element that was not found in B1. idx will be 0 for any element that was not found, and otherwise will be the index of the "first" location of the value in B1. idx will be a "linear index"

Answer 1

[madhan ravi]

https://in.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html - read it for better understanding

Linear_indices = find(ismember(B1,[26 4 28])); % you mean linear indices by saying single indices
B1(Linear_indices) % would give [26 4 28]

[Bruno Luong]

Careful about the order returned, and also duplication behavior, test with

B1=repmat([0 28 4 26]',1,4)

to see my points.

[madhan ravi]

True should have mentioned it, thanks sir Walter's approach above prevents it.

[Bruno Luong]

Yes so Walter should post his solution as answer and would be accepted.

[madhan ravi]

Ok so don't expect me to delete my answer though.

[Bruno Luong]

No IMO you should keep it. The difference is interesting to highlight.

Answer 2

[Walter Roberson]

[was_found, idx] = ismember([26 4 28], B1);

will assign to two variables: was_found and idx. was_found will be true for each element of [26 4 28] that was located somewhere in B1, and will be false for any element that was not found in B1. idx will be 0 for any element that was not found, and otherwise will be the index of the "first" location of the value in B1. idx will be a "linear index"