Array indices must be positive or logical values.

Hi,

I have a problem in converting my Fortran77 codes to MATLAB. Here are the equation of arrays that worked in FORTRAN77 but somehow showing "Array indices must be positive integers or logical values".

IDIM = 3000;
D = [-1:IDIM+2];
U = [-1:IDIM+2];
P = [-1:IDIM+2];
if IBCLEF == 0
    D(0) = D(1);
    U(0) = U(1);
    P(0) = P(1);
else
    D(0) = D(1);
    U(0) = -U(1);
    P(0) = P(1);
end
if IBRIGH == 0
    D(CELLS+1) = D(CELLS);
    U(CELLS+1) = U(CELLS);
    P(CELLS+1) = P(CELLS);
else
    D(CELLS+1) = D(CELLS);
    U(CELLS+1) = -U(CELLS);
    P(CELLS+1) = P(CELLS);
end

It will give me

Array indices must be positive integers or logical values.

Error in (line 6)
    D(0)=D(1);
    

I have been trying to look for solutions, but somehow I couldn't figure out the problems with setting up the array values.

Answer 1

[Ameer Hamza]

In MATLAB, the index of an array starts from 1 (as compared to many other languages where it starts from 0). Therefore, these lines should be something like this

D(1) = D(2);

Read about indexing here: https://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html

[Iman Fitri Ismail]

Thank you very much, it works!