# quiver to show the magnitude of velocity

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Changoleon on 25 Nov 2016
Edited: Changoleon on 25 Nov 2016
Hi all,
I have the following:
x=1;
y=1;
u=3;
v=4;
w = sqrt(u^2+v^2);
now if I use quiver(x,y,u,v) and click on the arrow by cursor, I will have x and y along with velocities in x and y axis are going to be shown. I want to my cursor to show the magnitude of the velocity which is w. For that I have watched the following video and tried to do the same job.
Following is what I have done:
function moneyplot(x,y,u,v)
fh = figure;
quiver(x,y,u,v,0)
dcm = datacursormode(fh);
datacursormode on
set(dcm, 'updatefcn', @myfunction)
end
function output_txt = myfunction(obj,event_obj,w)
pos = get(event_obj,'Position');
output_txt = {['velocity= ',w]};
if length(pos) > 2
output_txt{end+1} = ['Z: ',num2str(pos(3),4)];
end
However now every time I use the cursor to choose the arrow it shows : Error in custom datatip string function. Please see the picture below. What am I doing wrong? Will be apreciated for any kinda input.

Changoleon on 25 Nov 2016
Edited: Changoleon on 25 Nov 2016
I did not find the answer to my question. Here is what I have done and it kinda works, better than nothing
clc
x=[1 2 3 4 5];
y=[1 2 3 4 5];
u=[3 3 3 3 3];
v=[4 4 4 4 4];
quiver(x,y,u,v,0)
for i = 1:5
[xx,yy] = ginput(2);
velocity=sqrt((xx(2)-xx(1))^2 + (yy(2)-yy(1))^2);
strmin = ['Velocity = ',num2str(velocity),' m/s',[1 1 1]];
t = text(xx(1),yy(1),strmin,'HorizontalAlignment','left');
s = t.FontSize;
t.FontSize = 12;
end