oneByOneMatrix = 8

oneByOneMatrix =

     8

twoByTwoMatrix = [8 8; 8 8]

twoByTwoMatrix =

     8     8
     8     8

type changeOnlyOne8to9.m

function [output] = changeOnlyOne8to9( inputMatrix)
%changes only the first 8 to a 9 in a matrix and returns that altered matrix
%(The matrix is traversed row by row.)
%input: matrix
%output: matrix
     lengths = size(inputMatrix); %get size of matrix and store in 1x2 array
     eightNotSeenYet = true; %initialize flag to true
     m = 1; %initialize m to 1
     n = 1; %initialize n to 1
     disp(lengths(1));
     disp(lengths(2));
     while(eightNotSeenYet && (m <= lengths(1)))
         n = 1;
         while(eightNotSeenYet && (n <= lengths(2)))
             if  (inputMatrix(m,n) == 8) %if that position equals an 8
		 inputMatrix(m,n) = 9;  %change that position in the matrix to a 9 using an assignment statement
		 eightNotSeenYet = false; %set flag to false
                 fprintf('inside if: m and n are %d, %d\n', m, n);
             end  %ends the IF
	     fprintf('m and n are %d, %d\n', m, n);
             n = n + 1;
         end  %ends the inner While loop
         m = m + 1;
     end   %ends the outer While loop
	 fprintf('eightnotseenyet, m, n, %d %d %d', eightNotSeenYet, m, n);
     output = inputMatrix; %assign the matrix to the output value (or in other words, "return the (possibly) altered matrix")
end %end the function
     

changeOnlyOne8to9.m(oneByOneMatrix)
{??? Undefined variable "changeOnlyOne8to9" or class "changeOnlyOne8to9.m".
} 
changeOnlyOne8to9(oneByOneMatrix)
     1

     1

inside if: m and n are 1, 1
m and n are 1, 1
eightnotseenyet, m, n, 0 2 2
ans =

     9

changeOnlyOne8to9(twoByTwoMatrix)
     2

     2

inside if: m and n are 1, 1
m and n are 1, 1
eightnotseenyet, m, n, 0 2 2
ans =

     9     8
     8     8

%now, notice if we run it again, 
changeOnlyOne8to9(twoByTwoMatrix)
     2

     2

inside if: m and n are 1, 1
m and n are 1, 1
eightnotseenyet, m, n, 0 2 2
ans =

     9     8
     8     8

%the results are the same! Why?
%because we didn't assign the returned matrix to anything.
%Let's do that:
newMatrix = changeOnlyOne8to9(twoByTwoMatrix)
     2

     2

inside if: m and n are 1, 1
m and n are 1, 1
eightnotseenyet, m, n, 0 2 2
newMatrix =

     9     8
     8     8

newMatrix

newMatrix =

     9     8
     8     8

%now, we can input the newMatrix back in
newMatrix = changeOnlyOne8to9(newMatrix)
     2

     2

m and n are 1, 1
inside if: m and n are 1, 2
m and n are 1, 2
eightnotseenyet, m, n, 0 2 3
newMatrix =

     9     9
     8     8

%notice two nines are in the matrix now
%once more:
newMatrix = changeOnlyOne8to9(newMatrix)
     2

     2

m and n are 1, 1
m and n are 1, 2
inside if: m and n are 2, 1
m and n are 2, 1
eightnotseenyet, m, n, 0 3 2
newMatrix =

     9     9
     9     8

%and again:
newMatrix = changeOnlyOne8to9(newMatrix)
     2

     2

m and n are 1, 1
m and n are 1, 2
m and n are 2, 1
inside if: m and n are 2, 2
m and n are 2, 2
eightnotseenyet, m, n, 0 3 3
newMatrix =

     9     9
     9     9

%all the eights are now nines
diary off