simple MATLAB question ...

ok i am writting a code in which i need to write :

U(1,1) ,U (2,2) ,U (0,3) etc

and then i am going to assign some value to these separately...

for this purpose i use 2 "for" loops as follows:

for a=0:n-1 for b=0:n-1 where n i given a number by the user in the code.. and then i use U(a,b) ,so that it may write the points itself in each iteration....

but using this method matlab shows error that "U" is not defined function... am I writting it in correct way? if not then please help and correct it ...

thanx.

Answer 1

[Matt Fig]

MATLAB indexing starts at 1, not 0.

n = 5;
U = zeros(n);  % Pre-allocate the memory.
for a = 1:n
   for b = 1:n
      U(a,b) = a+b;
   end
end

[Ambreen]

will you please explain the line "U(a,b)=a+b" ?

[Matt Fig]

This assigns the value a+b to the matrix U at location (a,b). Run the code to see the result...

[Ambreen]

ok thanx,one more question ..you told indexing starts from 1,but what i should do to write U(0,1) ,U(0,2) etc????

[Matt Fig]

You simply cannot index into a MATLAB array with 0. In other languages (C++ for example) you can index into an array with 0, but not MATLAB. This will error. Look:

A = [1 2 4 6 8 9];

A(1)

A(2)

A(3)

A(0) % Error...

[Ambreen]

ok thanx