error: Array indices must be positive integers or logical values.

kw=0.6; L=1; do=0.06; di=0.05; B=330; kins=0.3; I=265; h=10:50;

m=(1/((kw(di)^2/(4*L))*((ln(do/di)/(2*kins))+(1/(h*do)))))^1/2;

[Margaret Wiersum]

why this error?

Answer 1

[Steven Lord]

m=(1/((kw(di)^2 ...

There's no such thing as element 0.05 of an array in MATLAB. Perhaps you're missing a multiplication sign there and you want to multiply kw and the square of di?

    /(4*L))*((ln(do/di)...

The function in MATLAB to compute the natural logarithm is log not ln.

/(2*kins))+(1/(h*do)))))^1/2;