Find index of last occurrence for each value

问题

I have a vector like this :

>> v = [1 1 1 2 2 3 4 4 4 4 4 5 5]'

v =

     1
     1
     1
     2
     2
     3
     4
     4
     4
     4
     4
     5
     5

The vector is sorted. There can be any number of each values. I need to find the index of the last occurence of each value. In this case, it would return this :

answer =

     3    % index of the last occurence of "1"
     5    % index of the last occurence of "2"
     6    % index of the last occurence of "3"
    11    % index of the last occurence of "4"
    13    % index of the last occurence of "5"

回答1:

Thanks to @trumpetlicks, the answer is unique.

>> v = [1 1 1 2 2 3 4 4 4 4 4 5 5 6]'

v =

     1
     1
     1
     2
     2
     3
     4
     4
     4
     4
     4
     5
     5
     6

>> [~, answer] = unique(v)

answer =

     3
     5
     6
    11
    13
    14

[EDIT] In more recente version of the MCR (R2013 ?), the behavior of unique has changed. To get the same result, you must use unique(v, 'legacy');

回答2:

v = [1 1 1 2 2 3 4 4 4 4 4 5 5];
find(v==1,1,'last')
 % returns ans = 3
find(v==2,1,'last')
 % returns ans = 5

the 1 gives the number of occurrences you want to return, and 'first' or 'last' may be specified

回答3:

Try this

[find(diff(v')) length(v)]

You should be able to figure it out yourself.

来源：https://stackoverflow.com/questions/11364920/find-index-of-last-occurrence-for-each-value