Change function myfind (index)

Question

Cristian 2014-5-11

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/129189-change-function-myfind-index

编辑： Cedric 2014-5-11

I wrote the function myfind that return index of key:

function index = myfind(vec, key)
len = length(vec);
index = 0;
for i = 1:len
if vec(i) == key
index = i;
end
end

How to change the function to return a vector of indices of all occurrences of the key?

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Answer 1

Cedric 2014-5-11

1
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/129189-change-function-myfind-index#answer_136410

编辑：Cedric 2014-5-11

在 MATLAB Online 中打开

Using the same approach as you developed so far, you would have to build index as a vector:

 index = [] ;
 for k = 1 : len
    if vec(k) == key
        index = [index, k] ;
    end
 end

Don't use i as a loop counter, because it should be reserved to complex notation. Now if you want to optimize a bit the approach, without using FIND, look at the following example:

 >> key = 3 ;
 >> vec = randi( 5, 1, 10 )
 vec =
     1     5     5     3     5     1     3     5     4     5
 >> isEq = vec == key
 isEq =
     0     0     0     1     0     0     1     0     0     0
 >> allInd = 1 : length( vec )
 allInd =
     1     2     3     4     5     6     7     8     9    10
 >> allInd(isEq)
 ans =
     4     7