MATLAB: Undefined function ‘m’ for input arguments of type ‘double

errortype 'double'undefined function

Hi, I don't know why I keep getting this error..I've made deep search on the forum but I got no solution.. Here's my function:
function [x,y,vx,vy,t] = ss(gx,gy,hx,hy,t0,tN,x0,y0,vx0,vy0,B,N)
%step size%
dt=(tN-t0)/(N-1);
%arrays%
t=linspace(t0,tN,N);
ax=zeros(B,N);
ay=zeros(B,N);
vx=zeros(B,N);
vy=zeros(B,N);
x=zeros(B,N);
y=zeros(B,N);
for i = 1:B
x(i,1)=x0(i);
y(i,1)=y0(i);
vx(i,1)=vx0(i);
vy(i,1)=vy0(i);
end
for i = 1:B % body number %
%Initial acceleration
for k = 1:N-1
for j = 1:B % rest of bodies%

if j==i %nothing%

else
ax(i,k)=ax(i,k)+gx(x(j,k)-x(i,k),y(j,k)-y(i,k),m(j));
ay(i,k)=ay(i,k)+gy(x(j,k)-x(i,k),y(j,k)-y(i,k),m(j));
end
end
%tmid = t(k)+dt/2;
xmid = x(i,k)+hx(vx(i,k)).*(dt/2); %????



ymid = y(i,k)+hy(vy(i,k)).*(dt/2); %????
vxmid = vx(i,k)+ax(i,k).*(dt/2);
vymid = vy(i,k)+ay(i,k).*(dt/2);
for j = 1:B % rest of bodies%
if j==i %nothing%
else
ax(i,k)=ax(i,k)+gx(x(j,k)-xmid,y(j,k)-ymid,m(j));
ay(i,k)=ay(i,k)+gy(x(j,k)-xmid,y(j,k)-ymid,m(j));
end
end
x(i,k+1) = x(i,k)+hx(vxmid).*dt; %????
y(i,k+1) = v(i,k)+hy(vymid).*dt; %????
vx(i,k+1) = vx(i,k)+ax(i,k).*dt;
vy(i,k+1) = vy(i,k)+ay(i,k).*dt;
end
end
Here's the script:
%Initial values
G=1 ;
B=2 ;
m=[40000;87777] ;
ax=zeros(B,1);
ay=zeros(B,1);
t0=0 ;
tN=365 ;
x0=[5;98765] ;
y0=[8975647;86] ;
vx0=[2;3] ;
vy0=[4,5] ;
N=10 ;
gx = @ (x,y,m) ((G.*m.*x)./(((x.^2)+(y.^2)).^(3/2)));
gy = @ (x,y,m) ((G.*m.*y)./(((x.^2)+(y.^2)).^(3/2)));
hx = @ (x,y,m) (vx);
hy = @ (x,v,m) (vy);
[x,y,vx,vy,t] = ss(gx,gy,hx,hy,t0,tN,x0,y0,vx0,vy0,B,N);
And the error is…
Undefined function 'm' for input arguments of type 'double'.
Error in ss (line 27)
ax(i,k)=ax(i,k)+gx(x(j,k)-x(i,k),y(j,k)-y(i,k),m(j));
Thanks in advance!

Best Answer

You have a reference to m(j) in the subject line but there's no definition of a variable m in the function nor is it in the argument list. Hence, to Matlab the expression m(j) looks like a function which you don't have one of, either.
If (as I presume) it's intended to be an array of masses (given the comment on acceleration and bodies), then pass it as another argument.