find observations with nonconsecutive numbers

A=[55; 56; 57; 58; 26; 27; 28]

I want to find the observations in A where the two consecutive observations are not equal. In this case it should be the 5th observation since 26~=58. How can I do that elegantly?

Answer 1

[Walter Roberson]

find(diff(A) ~= 1) + 1

Answer 2

[JESUS DAVID ARIZA ROYETH]

like this:

A=[55; 56; 57; 58; 26; 27; 28];
observations=A([1; diff(A)]~=1);

[wesso Dadoyan]

these codes are giving 26 instead of 5. I don't want the value but rather the row number.

[JESUS DAVID ARIZA ROYETH]

A=[55; 56; 57; 58; 26; 27; 28];
observations=find([1; diff(A)]~=1);