I am trying to calculate normalized root square error (NRMSE) between my optical flow estimation and the provided ground truth I think I calculated the RMSE correctly, However, the normalized always INF values !

Here is part of my code: 

% u , v ==> estimated flow % cu , cv ==> ground truth flow du=abs(u-cu); dv=abs(v-cv); % To compute Absulet error AE= sqrt(du.^2+dv.^2); AE_aver= mean (AE(:)); % To compute End Point Error EPE=mean(AE(:)); % To Compute Root Mean Square Error X=AE.^2; RMSE=sqrt(mean(X(:))); % To Compute Normalized Root Mean Square Error Vg=cu.^2+cv.^2; xx=max(Vg(:)); nn=min(Vg(:)); NRMSE=RMSE./( xx - nn );

Could you please show me where is my mistake? thank you 

Answer: 

The only way that NRSME can be Inf is if either RMSE is Inf or (xx-nn) = 0.

So, you need to check your data. Either cu and cv are both constant (either scalar constants, or vectors with the same value in every element), which would lead to (xx-nn) = 0, or at least one of u, v, cu or cv has at least one entry that is Inf, which would lead to RMSE being Inf.