How can I replace string categories into numbers (such as 'AAA' would become 1, 'AA+' would become 2)?

I found how to create a categorical array from integers but I'm trying to do the opposite as I want to calculate with the ratings.

[Azzi Abdelmalek]

Can you post an example?

[Peter Perkins]

Although Sean has answered your specific question, needing to convert a categorical to numbers is sometimes an indication that maybe you are trying to do something that could be done another way, or something that categorical isn't really intended for. Can you provide more context?

[Jelle Zwart]

Sean's answer is exactly what I was looking for. I'm calculating an average rating for a number of bonds. So first I'm retrieving the individual ratings for those bonds (S&P, Moody's, Fitch). After turning them into categorical arrays,

B = categorical(BondRatings);

merging categories

oldcats = {'A-','A- /*+','A- /*-','A- /*'};
B = mergecats(B,oldcats);

and setting the possible categories

 catnames = {'AAA','AA+','AA','AA-','A+','A','A-','BBB+','BBB','BBB-','BB+','BB','BB-','B+','B','B-','CCC+','CCC','CCC-','CC','C','D'};
 A = setcats(A,catnames);

I need to convert them to numbers to calculate the mean. Afterwards I do exactly the opposite: I transform the means into categories

valueset = [1:22];
Ratings = [double(S_P),double(Moody),double(Fitch)];
FinalRating = categorical(round(nanmean(Ratings,2)),valueset,catnames);

Answer 1

[Sean de Wolski]

double(categorical_array)