[R] RMSE vs. RMSD

[Taka Matzmoto]

Hi R users
This is not related to R but general stats terms. I

f any one help me to figure out how they differ and when I need to use which 
one, i will appreciate it.

I read several simulation studies and found that RMSE (Root Mean Square 
Error) and RMSD (Root Mean Square Difference) appered to be used 
interchangeablely. The formula for calculating for both RMSE and RMSD are, 
to me, the same. Are they the same or am I misunderstood ?

TM