Streamlines to visualize 6-component Electromagnetic data

I am having trouble understanding and using the streamlines fucntion

I have 6-component electromagnetic data. ie. Ex,Ey,Ez & Hx,HyHz.

X = RX_Mesh;
Y = RY_Mesh;   %Km
Z = RZ_Mesh;

 startx = X(51:10:101);
 starty = Y(101:10:201);
 startz = Z(51:10:101);

freq=1

%VECTOR COMPONENTS
ex = Ex;    ey = Ey;    ez = Ez;   %electric vector components
hx = Hy_Total;    hy = Hy_Total;    hz = Hz_Total;    % magnetic vector components
u3 = Sx;    v3 = Sy;    w3 = Sz;                                     %poynting vector components

close all
streamline(X,Y,Z,ex,ey,ez,startx,starty,startz)
 hold on
 streamline(X,Y,Z,hx,hy,hz,startx,starty,startz)

using all other functions such as slice, contour, quiver3 etc my data plots as expected so it cannot be the data. I am just not understanding something correctly about the startx,starty,startz