How to solve "index exceeds the number of array elements"

Hi,

Why I can't plot the following code? The error is: Index exceeds the number of array elements (1).

What I'm trying to achive is that a user enters a scalar value f (such as 1500) anf Ht and Hr. So, I want to find value of ahr and L accondingliy and then plot L vs f. SO on f axis I shoud have 100,150,200,250,300,....,1500 and corrsponding values on L axis.

for i=100:50:f
        cm=0;
        ahr(i)=(1.1*log10(f(i))-0.7)*Hr-1.56*log10(f(i))-0.8;
        L(i)=46.3+33.9*log10(f(i))-13.82*log10(Ht)-ahr+(44.9-6.55*log10(Hr))*log10(d)+cm;
        plot(f,L)
        end

Answer 1

[Mischa Kim]

Hi Ryan, try something like this:

fl = 100;
fu = 1500; % replace as necessary 
N  = 100;
f  = linspace(fl,fu,N);
cm = 0;
for ii = 1:numel(f) % careful with "i", this is also the imaginary unit
    ahr(ii) = (1.1*log10(f(ii))-0.7)*Hr-1.56*log10(f(ii))-0.8;
    L(ii)   = 46.3+33.9*log10(f(ii))-13.82*log10(Ht)-ahr(ii)+(44.9-6.55*log10(Hr))*log10(d)+cm;
end
plot(f,L)

[Ryan Majid]

Thank you. This is exactly what I needed. However, would you please explain it more. I mean what was wrong with my code. Is that cus of f was not a vector?

[Mischa Kim]

With

for i=100:50:f

i is assigned values: 100, 150, 200, 250, etc. As a result, in

L(ii) = 46.3+33.9*log10(...

you create a (rather long) vector L and assign values to L(100), L(150), and so on and so forth. At the same time, f is a scalar (just one number). For the plot() command to work f and L need to be vectors of the same size.

[Ryan Majid]

Understood. So appreciated.