calculating a few elements of a table, using a different equation

Hello!

Let's say that i am calculating every element of a 100X300 table by using equation A I use two for loops for i=1:100 for j=1:300 element(i,j)=... (it is the equation A) end end equation A involves the neighboring elements What if, a few elements of the table must be calculated with a different equation, equation B and this must happen inside the two for loops

for example elements (49,81) (49,82) (50,81) (50,82) (51,81) (51,82) (52,81) (52,82) i could use if and elseif function for every single element, like if i==49 && j==81 element(i,j)=...equation B elseif i==50 && j==81 element(i,j)=...equation B ...

...

end Is there another, better way to do it ???

Thanks a lot!

Answer 1

[Andrei Bobrov]

a = 49:52
b = 81:82
ii = fullfact([numel(b) numel(a)])
for jj = 1:size(ii,1)
    element(a(ii(jj,2)),b(ii(jj,1))) = ...equation;
end

or

[b1,a1] = ndgrid(b,a);
ii = a1(:);
jj = b1(:);
for ij = 1:numel(ii)
    element(ii(ij),jj(ij)) = ...equation;
end

[vaggelis vaggelakis]

Thanks Andrei!

But i want this to be executed only when i and j indices are pointing to the listed elements,(49,81) (49,82) (50,81) (50,82) (51,81) (51,82) (52,81) (52,82)

the table i calculate has 101X301 elements and is named T. So

for i=1:101

for j=1:301

T(i,j)=...equation A

end

end

when i=49 and j=81 i want to calculate this point with equation B inside these two "for" loops!

I think, what you sent me is going to be executed on every iteration in these loops while i want equation B being executed ONLY when i,j are referring to these few predefined elements

I already tried to use "ismember" function, it worked but my code was significantly slower!

I also tried "if-ifelse" function for every each one of these elements(equation B) following by "else" for all the others (equation A). It works fine, but i m looking for a better code!

[vaggelis vaggelakis]

I forgot to mention that all the calculations are implicating the neighboring elements, that's why i am calculating element by element and the "equation A" elements can't be calculated without the "equation B" inside the loops!