Undefined function 'm' for input arguments of type 'double

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!

Answer 1

[dpb]

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.

[Oscar García]

Yeah, I can see it now, damn... Thank you very much!

[Oscar García]

Unfortunately I'll probably have more errors...

Answer 2

[James Tursa]

Error seems straight forward to me ... once you reach that line m is not defined, hence the error. Is m supposed to be a vector containing the mass of the objects, and you forgot to define it?