Error: Unable to perform assignment because the left and right sides have a different number of elements.

Here's my code:

r = input("Inserta el radio:");
densidad = 1.225;
vol = (4/3)*pi*(r^3);
dt = 0.002;
m = 0.000000796
g = 9.8;
A = 0.00008;

%constantes:
b = 0.000115454

%metodo de euler:
yinicial = 0;
yfinal = 1;
y = yinicial : dt : yfinal;
N = length(y);

x(1) = 0
x = zeros(1,N)
vf = zeros(1,N)
vf = input("Ingresa velocidad:")
vf(1) = vf

for a = 1: (N-1)
    vf(a+1) = ((-g)+((p-A*a)*(vol*g)/m)-((b*vf)/m))*dt+vf;
end
for a = 1: (N-1)
    p(a+1) = p(a)+(dt*vf(a))
end
 hold on
 plot(y,vf,'r')
 title("Velocidad vs tiempo")
 plot(y,p, 'b')
 title("Posicion vs tiempo")

[Alejandra Caballero]

The error is in the line of vf(a+1) = ((-g)+((p-A*a)*(vol*g)/m)-((b*vf)/m))*dt+vf; btw

Answer 1

[KSSV]

for a = 1: (N-1)
    vf(a+1) = ((-g)+((p-A*a)*(vol*g)/m)-((b*vf(a))/m))*dt+vf(a);
end

[Alejandra Caballero]

sadly I got a new error after that, "array indices must be positive integers or logical values." )):

[KSSV]

Yes....my typo error...the loop index is a not i. Edited the answer. Check.

[Alejandra Caballero]

I tried it and it showed me the previous error ("Unable to perform assignment because the left and right sides have a different number of elements.") Again! )):

[KSSV]

You define all the variables...and copy the code.....I tried running it..but few variables are missing.

This error comes..when you try to store a array into a scalar.

Example:

c(1) = rand(1,2) ; % this shows error. Samething happening in your code

Check the size of

((-g)+((p-A*a)*(vol*g)/m)-((b*vf(a))/m))*dt+vf(a);

it might not be a constant.