Condition for matlab if

[d,g] = max(Wscat,[],1);
for i = 1:length(d)
        if g(i)+20>size(Wscat,1);
        PP=Wscat((g(i)-50:g(i)),i) ;
        P{i}=PP(PP ~= 0);
        
    elseif g(i)-50<0       % condition when g = 1 minus 50
        PP=Wscat(1:g(i),i) ; % In my matrix, some values ​​are g = 1 and 1-50
        P{i}=PP(PP ~= 0);
        
    else 
        PP=Wscat((g(i)-50:g(i)),i) ;  % Error Subscript indices must either be real positive integers or logicals.
        P{i}=PP(PP ~= 0);
        
end

end

Error Subscript indices must either be real positive integers or logicals.

How to fix this problem?

Answer 1

[infinity]

Hello

How about if you remove semi-colon in the line

if g(i)+20>size(Wscat,1);

[Lev Mihailov]

Deleted, I think it is worth making a cycle if less than 20 then = g + 21, if more then f

[d,f] = max(Wscat,[],1);
for i = 1:length(d)  
    if f(i)>20
        g(i)=f(i)
    else f(i)<20
         g(i)=f(i)+21
    end
    
end

But I do not understand why my cycle does not work?

[infinity]

I think should refer answers below since g(i) - 50 may less than or equal to 0. Then, you should think how to modify the condition statement in "if - elseif - else".

Answer 2

[Steven Lord]

PP=Wscat((g(i)-50:g(i)),i) ;

If g(i) is exactly equal to 50, this will ask for the 0th element of Wscat. Arrays in MATLAB don't have 0th elements; the first element is 0. 0 is not a "real positive integer".

Does your data ever have g(i) exactly equal to 50? Does it reach this section of your if/elseif/else construct if it does?

Answer 3

[Star Strider]

I suspect that here:

PP=Wscat((g(i)-50:g(i)),i) ;  % Error Subscript indices must either be real positive integers or logicals.

the result of:

g(i)-50

is going to be negative or 0, neither of which are allowed in MATLAB subscripts.

Without knowing what those values are, it is not possible to write specific code to correct the problem.