??? Attempted to access vv(:,1); index out of bounds because size(vv)=[0,0] - Help?

Hi,I was hoping somebody would be able to help.

I keep getting this error when running this small program and I have absolutely no idea why:

??? Attempted to access vv(:,1); index out of bounds because size(vv)=[0,0].

Error in ==> interpstreamspeed at 104 spdi = interp2(x,y,spd,vv(:,1), vv(:,2));

if true
  % x and y values;
clc;
clear all;
x = -19.5:1:19.5;
y = 0.5:1:14.5;
[xgrid ygrid] = meshgrid(x,y);
A = 1;
sx = [-20:1:20];
sy =linspace(10,10,41)
% x Component;
u = A.*(xgrid);
% y Component;
v = A.*(-ygrid);
% Plotting Streamlines;
verts = stream2(xgrid,ygrid,u,v,sx,sy);
streamline(verts)
hold all;
% Plot straight thick lines;
h = plot(x,0,'*k');
set(h,'linewidth',2);
% Animate particles along streamlines;
iverts = interpstreamspeed(xgrid, ygrid, u, v, verts,0.01);
streamparticles(iverts,20,'Animate',2,'FrameRate',100);
end

Could anybody possibly tell me why?

Thank You, Chris

[Walter Roberson]

Are you sure you want your sy = linspace(10,10,41) ? That would be 41 copies of the value 10 ?

[Matt J]

Since the error occurs inside interpstreamspeed (according to the messages), you need to show the contents of that function.

[Matt Fig]

Matt J, that function is a MATLAB function.