Illustration of logical built-in functions:

The function find returns the indices of a vector which meet certain criteria. For illustration, to find all the elements in a vector which are greater than 5:

>> vec = [5 3 6 7 2]

vec =

  5  3  6  7  2

>> find(vec > 5)

ans =

     3   4

The function is also equal and is useful in comparing the vectors. In MATLAB, using the equality operator with arrays will return 1 or 0 for every element; the all function could then be used on the resulting array to establish whether all elements were equal or not. The built-in function is equal and it also accomplishes this:

>> vec1 = [1 3 -4 2 99];

>> vec2 = [1 2 -4 3 99];

>> vec1 == vec2

ans =

1  0  1  0  1

>> all(vec1 == vec2)

ans =

0

>> isequal(vec1,vec2)

ans =

0