Unable to perform assignment because the left and right sides have a different number of elements. Error in Hyperverlocitynew (line 36)

n=1000; %number of iterations 

x=zeros(n); % horizontal distance traveled
y=zeros(n); % vertical distance traveled
vx=zeros(n); % horizontal velocity
vy=zeros(n); % vertical velocity
v=zeros(n); % total velocity

theta_th=0.6575; % launch angle
vx(1)=7815.06*cos(theta_th); % starting x velocity
vy(1)=7815.06*sin(theta_th); % starting y velocity
x(1)=0; % starting x position 
y(1)=0; % starting y position
delta_t=0.0001; % step size
a=(pi/4)*(3/12)^2; % area of projectile
m=55/32.174; % mass of projectile
g=32.174; % gravity
k=1.4; % 
R=1716.5; % ideal gas constant



for i=2:n
   
    [T,p,rho]=atmos_funEE; %
    c=sqrt(k*R*T); % speed of sound
    ma=v(n)/c; %
    if (0<ma)&&(ma<=0.8) %
    cd=0.17; %
    elseif (0.8<ma)&&(ma<=1.2) %
    cd=0.7763*ma-0.451; %
    elseif (1.2<ma)&&(ma<=8) %
    cd=0.0093*ma^2-0.1223*ma+0.607; %
    end
    x(i)=(x(i-1))+(delta_t*(vx(i-1))); %
    vx(i)=(vx(i-1))+(delta_t*(-1/2)*rho*a*cd*(v(i-1))*(vx(i-1))*(1/m)); %
    y(i)=(y(i-1))+(delta_t*(vy(i-1))); %
    vy(i)=(vy(i-1))+(delta_t*(-g-(1/2)*rho*a*cd*v(i-1)*(vy(i-1))*(1/m))); %
    v(i)=sqrt((vx(i-1))^2+(vy(i-1))^2); %
end 

[Alan Stevens]

What's in atmos_funEE?

[James Murray]

It’s a function that calculates the coefficient of drag as a projectile is shot in the air. the function uses altitude to calculate this.

[Alan Stevens]

I've just noticed that you have defined x, y, etc. as zeros(n). This will result in matrices of size nxn for each of them. Is this what you meant, or did you mean zeros(1,n), which will result in vectors of size 1xn?

[Walter Roberson]

You are not passing anything into the function. How can it be calculating correct coefficients?

The current hypothesis is that rho is a non-scalar

Answer 1

[Rohit Pappu]

As per my understanding, you are unable to assign the value of the equation to vx(i). The error might have occurred because the variable cd is declared conditionally and thus it behaves like a matrix.

A plausible solution would be to declare cd outside the loop which would make the variable remain as a scalar.