Error: Array indices must be positive integers or logical values

Hi! I'm getting a error that says "Array indices must be positive integers or logical values" about "Vmin=min(V) when running the code below:

m=100;

l=5;

k=200;

g=9.82;

o=[0:0.01:90]; %θ

V=0.5*k*l^2*(sind(o)).^2+0.5*m*g*l*cosd(o);

plot(o,V);

title("V(θ)");

xlabel("θ[°]");

ylabel("V[J]");

Vmax=max(V);

indexMax=find(V==Vmax);

oForVmax=o(indexMax(1));

Vmin=min(V);

indexMin=find(V==Vmin);

oForVmin=o(indexMin(1));

disp(Vmax);

disp(oForVmax);

disp(Vmin);

disp(oForVmin);

I don't really understand why because V will not be zero or negative.

Answer 1

[Image Analyst]

The code you posted runs fine with no errors.

In general see the FAQ:

https://matlab.fandom.com/wiki/FAQ#%22Subscript_indices_must_either_be_real_positive_integers_or_logicals.%22

m=100;
l=5;
k=200;
g=9.82;
o=[0:0.01:90]; %θ
V=0.5*k*l^2*(sind(o)).^2+0.5*m*g*l*cosd(o);
plot(o,V);
title("V(θ)");
xlabel("θ[°]");
ylabel("V[J]");

Vmax=max(V);
indexMax=find(V==Vmax);
oForVmax=o(indexMax(1));
Vmin=min(V);
indexMin=find(V==Vmin);
oForVmin=o(indexMin(1));
disp(Vmax);

   3.1027e+03

disp(oForVmax);

   60.5900

disp(Vmin);

        2455

disp(oForVmin);

     0

[David Hill]

You might want to clear all your variables before you execute the script.

Answer 2

[David Hill]

Runs without error

m=100;
l=5;
k=200;
g=9.82;
o=[0:0.01:90]; %θ
V=0.5*k*l^2*(sind(o)).^2+0.5*m*g*l*cosd(o);
plot(o,V);
title("V(θ)");
xlabel("θ[°]");
ylabel("V[J]");

Vmax=max(V);
indexMax=find(V==Vmax);
oForVmax=o(indexMax(1));
Vmin=min(V);
indexMin=find(V==Vmin);
oForVmin=o(indexMin(1));
disp(Vmax);

   3.1027e+03

disp(oForVmax);

   60.5900

disp(Vmin);

        2455

disp(oForVmin);

     0