reading strings with if statements

Hi I have the following:

clc

clear

matrix=[1 2 3 4;5 6 7 8;9 10 11 12;13 14 15 16];

letter='da';

if letter(1)=='a'

      pos1=matrix(1,1)+matrix(1,3);

elseif letter(1)=='b'

      pos1=matrix(2,1)+matrix(2,3);

elseif letter(1)=='c'

      pos1=matrix(3,1)+matrix(3,3);

elseif letter(1)=='d'

      pos1=matrix(4,1)+matrix(4,3);

if letter(2)=='a'

      pos2=matrix(1,1)+matrix(1,3);

elseif letter(2)=='b'

      pos2=matrix(2,1)+matrix(2,3);

elseif letter(2)=='c'

      pos2=matrix(3,1)+matrix(3,3);

elseif letter(2)=='d'

      pos2=matrix(4,1)+matrix(4,3);

end

disp(matrix)

disp(pos1)

disp(pos2)

This cannot be evaluated by MATLAB any clues?

[KA]

Thank you Geoff.

Answer 1

[Geoff Hayes]

Antoni - you are missing an end after the third elseif just prior to the next if

 elseif letter(1)=='d'
      pos1=matrix(4,1)+matrix(4,3);
 end                                     %<-----missing end
 if letter(2)=='a'

You need to end the first if and elseif block before you begin a new one.