Unable to perform assignment because the left and right sides have a different number of elements(funtion in a while loop).

I am trying to run a function that i've made inside a while loop to get answers out of the funtion multiple times, but i get the following error:

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

Error in spere_derive_2d_call (line 21)

[slope_xg(i),slope_vxg(i),slope_yg(i),slope_vyg(i)]=spere_derive_2d(vx,vy,Cd,Dsg,msg,rho);

After trying to debug i found that it happens on my second time through the loop. I'm not even sure what the left and right side are in relation to being in a funtion call, nor why they would need to have the same number of elements.

v0=25;
theta=30;
dt=.001;
rho=1.225;
Cd=0.5;
Dsg=0.04;
msg=0.045;
vx=v0*cosd(theta);
vy=v0*sind(theta);
i=2;
xg(1)=0;
yg(1)=0;
check=1;
while check>=0
[slope_xg(i),slope_vxg(i),slope_yg(i),slope_vyg(i)]=spere_derive_2d(vx,vy,Cd,Dsg,msg,rho);  %this is the problem line
vx=slope_yg;
vy=slope_yg;
yg(i)=slope_yg(i)*dt+yg(i-1);
xg(i)=xg(i-1)+slope_xg(i)*dt;
check=yg(i);
i=i+1;
end

Answer 1

[Voss]

I don't have the function spere_derive_2d, so I can't run the code, but I guess that spere_derive_2d returns at least 4 outputs, which you are attempting to store as slope_xg(i), slope_vxg(i), slope_yg(i), and slope_vyg(i), respectively.

The problem (and what the error message is saying) is that at least one of those outputs from spere_derive_2d is not a scalar (i.e., 1-by-1 in size), so it cannot be stored as a single element of an array, e.g., slope_xg(i).

[josiah]

Thank you, this was it. I changed vx=slope_yg; and vy=slope_yg; to vx=slope_yg(i); and vy=slope_yg(i).

[Voss]

You're welcome!