I need to read a sequence and convert it t0 numerical text

Can any body help me to find a solution.My objective is to convert a dna sequence into numerical form ie A with 1, C with 2, T with 3 and G with 4.hcv is a structure having two fields header and sequence. when i tried to display it is not showing any ouput, no errors.the code is given below.Eg of sequence ACTTTGGCTT.........

s1='A';s2='C';s3='T';s4='G';
n=10;%%%%%%%%number of sequences%%%%%%
hcv = fastaread('hcv1.fas','IgnoreGaps',true);

hcvnum=hcv;
for i=1:n
len(i) = cellfun(@length, {hcv(i).Sequence});
    for j=1:len(i)
        if strcmp(hcv(i).Sequence(j),s1)
            hcvnum(i).Sequence(j)=1;
        elseif strcmp(hcv(i).Sequence(j),s2)
            hcvnum(i).Sequence(j)=2;
        elseif strcmp(hcv(i).Sequence(j),s3)
            hcvnum(i).Sequence(j)=3;
        else
            strcmp(hcv(i).Sequence(j),s4)
            hcvnum(i).Sequence(j)=4;
        end
    end
end

Answer 1

[Walter Roberson]

      for j=1:len(i)
        [tf, idx] = ismember(hcv(i).Sequence(j), {s1,s2,s3,s4});
        if tf; hcvnum(i).Sequence(j) = idx; end
        %if tf is false then it was some other character
      end