How to enumerate an array?

I want a simple enumeration of the following series a=

['465465465','465465465','465465465','31546895489','31546895489','897897979','897897979', '897897979','897897979','897897979','897897979')'

in order to get

   b=(1,1,1,2,2,3,3,3,3,3,3);

I tried with

b(1:length(a))=1;
for i=2:length(a)
if isequal(a(i),a(i-1));
b(i)=b(i-1);
else
b(i)=i+1;
end
end

(but that is not the expected result)

Answer 1

[Star Strider]

Create it as a cell array, and use unique. It will give you almost what you want, however unique sorts the results, so they will not be exactly in the order you specified:

a={'465465465','465465465','465465465','31546895489','31546895489','897897979','897897979', '897897979','897897979','897897979','897897979'}';
[as,~,ic] = unique(a);

The ‘as’ vector gives you the sorted results, and ‘ic’ will give the corresponding indices in the order they appear in ‘a’.

[Konstantinos Sofos]

I agree with the above solution with a small remark. If you want to have your b vector exactly in the order that you asked you should use

[~,~,b] = unique(a,'stable')

then the result will be

b =

      1     1     1     2     2     3     3     3     3     3     3

[Star Strider]

Forgot about 'stable'. Thanks!

Answer 2

[Aleksandar]

Thank you!!

[Star Strider]

My pleasure!