Index error: must be logical or positive integer.

T=10:2:60;
f=-1:length(T)+1;
total=-1;
i=f+total;
et=3.5e-4;
dn1=1e-9:100e-9;
if i==0
    r=0;
else
   % r=(et+((dn1(i+1)-dn1(i))))./((dn1(i)-(dn1(i-1)))+et); upwind and lower
   % wind
    r=(et+((dn1(i+1)-dn1(i))))./((dn1(i)-(dn1(i-1)))+et);
end

Array indices must be positive integers or logical values.

[DGM]

Is i a positive integer or logical value?

Answer 1

[Askic V]

T=10:2:60;
f=-1:length(T)+1;
total=-1;
i=f+total;
et=3.5e-4;
dn1=1e-9:100e-9;
size(dn1)

ans = 1×2

1 1

size(i)

ans = 1×2

1 29

if i==0
    r=0;
else
   % r=(et+((dn1(i+1)-dn1(i))))./((dn1(i)-(dn1(i-1)))+et); upwind and lower
   % wind
    r=(et+((dn1(i+1)-dn1(i))))./((dn1(i)-(dn1(i-1)))+et);
end

Array indices must be positive integers or logical values.

I hope you can see where the error is.