array index

Hi, I have declared the size of array as 4*4.When i run the third for loop the size of array becomes 49*49.Dont know why this happens in that loop?

pat1='11';
arr=zeros(4,4);

   len=length(pat1);
   for i=1:4
      for j=1:4
          arr(i,j)=l+2;
      end
  end

for j=1:4
    arr(1,j)=1;
end
for i=1:len-1
    arr(pat1(i),pat1(i+1))=l-i;

end
for i=1:4
    arr(i,1)=l+1;
end

[EDITED, Jan Simon, Code formatted]

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup

Answer 1

[the cyclist]

Because "pat1" is a character array, you are accessing the numerical equivalent of the character '1', which is 49. MATLAB is implicitly using "double('1')" to convert that character to a numeric.

Not sure why you defined pat1 that way, but you could use the following in your third loop:

arr(str2num(pat1(i)),str2num(pat1(i+1)))=l-i;

(If that is indeed what you intend.)

[Rakshmy C S]

Now its working, Thanks a lot

[the cyclist]

It would be helpful if you were to "Accept" an answer, signaling to future users that the Question was answered.

[Walter Roberson]

But what if the pattern did not happen to correspond to numeric characters?

If you are *sure* that pat1 will contain only numeric characters, then the str2num() calls that the cyclist shows can be replaced:

arr(pat1(i)-'0', pat1(i+1)-'0') = 1-i;

Answer 2

[Walter Roberson]

49 is the numeric equivalent of the character '1' . You are trying to index your array "arr" at the character pat1(i)