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I am working on a project to convert a large Fortran77 code into MATLAB. Since Do loops in F77 are equivalent to For loops in MATLAB, a subroutine of F77 when translated into MATLAB is giving error. The F77 subroutine is given in link[^]


and my tried MATLAB translated version is given in "What I have tried" section
which is giving following error

Attempted to access G(0); index must be a positive integer or logical

 HS(i)=FI^(NH)*G(2*i)/(G(NH-i)*G(i)*G(i-1));


I  think I am unable to understand complex loop structure present in subroutine of Fortran77.

What I have tried:

G(1)=1.0;
NH=NS/2;
for i=2:NS
       G(i)=G(i-1)*i;
end
HS(1)=2.0/G(NH-1);
for i = 2:NH
      FI=i;
      if i== NH
              HS(i)=FI^(NH)*G(2*i)/(G(i)*G(i-1));
     end
     HS(i)=FI^(NH)*G(2*i)/(G(NH-i)*G(i)*G(i-1));
end
SN=2*(NH-NH/2*2)-1;
   for i=1:NS
       V(i)=0.0;
      K1=(i+1)/2;
      K2=i
      if K2 > NH
           K2 = NH;
      end
      for j=K1:K2
          if 2*j-i == 0
                   V(i)=V(i)+HS(j)/(G(i-j));
          elseif i == j
                  V(i)=V(i)+HS(j)/G(2*j-i);
          end
     end
   V(i)=SN*V(i);
   SN=-SN;
end
Posted
Updated 27-Apr-16 1:23am
Comments
Richard MacCutchan 24-Apr-16 9:06am    
Looks like you initialise sets from 1 to N, but then try to access item 0 which does not exist.

1 solution

C#
G(1)=1.0;
NH=NS/2;
for i=2:NS
    G(i)=G(i-1)*i;
end
HS(1)=2.0/G(NH-1);
    for i = 2:NH
        FI=i;
        if i== NH
                HS(i)=FI^(NH)*G(2*i)/(G(i)*G(i-1));
          else
                 HS(i)=FI^(NH)*G(2*i)/(G(NH-i)*G(i)*G(i-1));
          end  
    end
    SN=2*(NH-NH/2*2)-1;
    for i=1:NS
        V(i)=0.0;
        K1=floor((i+1)/2);
        K2=i;
        if K2 > NH
            K2 = NH;
        end
        for j=K1:K2
          if 2*j-i == 0
                V(i)=V(i)+HS(j)/(G(i-j));
          elseif i == j
                 V(i)=V(i)+HS(j)/G(2*j-i);
          else
              V(i)=V(i)+HS(j)/(G(i-j)*G(2*j-i));
          end  
        end
        V(i)=SN*V(i);
        SN=-SN;
    end
 
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