Error: Array indices must be positive integers or logical values

%% Inputs

Q = 0.16; %[m^3/s] flowraten

r_2 = 0.25; %[m]Ydre radius

D_2 = 0.50 %[m]Ydre diameter

b_2 = 0.5 %[m]Blad højden

beta_2 = 75 %[grader] vinklen

U_2 = (r_2 * omega) * 2*pi * 1/60

%Head

H_plot = zeros(50,1);

for Q = 1:1:50;

H = (U_2^2*Q/g - U_2/(pi*D_2*b_2*g*tand(beta_2))); % [m] Beregning af head

H_plot(i)= H;

i = i+1;

end

why do i get this error message: Array indices must be positive integers or logical values

[Stephen23]

"why do i get this error message: Array indices must be positive integers or logical values"

Because you do not define i, and so it defaults to the imaginary unit (which is not a valid index).

Note that it is usually much clearer to loop over an index variable rather than looping over data (e.g. Q). Note that you define Q twice in your code, which is unlikely to be intentional.

Most likely you can replace that loop with vectorized code:

https://www.mathworks.com/help/matlab/matlab_prog/vectorization.html

[Trine Høy Oddershede]

(y)

Answer 1

[KALYAN ACHARJYA]

Q = 0.16;            %[m^3/s] flowraten
r_2 = 0.25;          %[m]Ydre radius
D_2 = 0.50          %[m]Ydre diameter
b_2 = 0.5            %[m]Blad højden
beta_2 = 75         %[grader] vinklen 

%Define Omega and g

omega=
g=

Remaining code (Loop can be avoided here)

U_2=(r_2 * omega) * 2*pi * 1/60
Q = 1:1:50;
H = (U_2^2*Q./g - U_2/(pi*D_2*b_2*g*tand(beta_2)));          
plot(H,Q);

[Trine Høy Oddershede]

(y)