finding most common letter in a string

say I have a string y='asdqwdqwdasasdasdaasasdwdqwd' How do I find the letter that occurs the most in y which is clearly 'a' so have something like mostcommonletter='a'

Answer 1

[Azzi Abdelmalek]

y='asdqwdqwdasasdasdaasasdwdqwd'
[ii,jj,kk]=unique(y)
a=accumarray(kk,1)
idx=a==max(a)
out=ii(idx)