Question

Im extracting frames from video and plotting the slope value for the coordinates obtained in each line detected in each frame like below

Am plotting the “slope” value against “frames”.

Extracting frames from video

for k = 1 :240 %no.of frames
%Here in loop am extracting the line from each frame then 
[ycoord,xcoord]=find(line);%finding the coordinates of line
Ymax(k)=max(ycoord); 
Ymin(k)=min(ycoord); 
Xmax(k)=max(xcoord); 
Xmin(k)=min(xcoord); 
slope(k)=(Ymax(k)-Ymin(k)/Xmax(k)-Xmin(k));
end; 
plot(slope,'-ro');%plotting slope values of frames 

But when there is no line found in a frame then find(line) is giving empty arrays and there is no slope calculated showing error .
My requirement is when there is no line in the next frame then the slope value should be zero else it should calculate the slope value.
can some one please help on this

Answer 1

I don’t really understand your code, but in general, when find can’t find something, it returns an empty matrix. You can use the isempty function to test if this is the case and manually set ycoord and xcoord to values that won’t cause an error on.

isempty() MATLAB Documentation

Hope this helps!