My data includes prediction results from a multivariate model, from which I would like to compute the RMSEP, that is, the root mean squared error of prediction:
RMSEP = sqrt( (1/N) * sum( (computed - measured)^2 ) )
To simplify, I first create a new calculated measure 'Residual_Squared' as (computed - measured)^2
but, this calculation:
WINDOW_SUM([Residual_Squared])
is flagged, saying 'All fields must be aggregate or constant when using table calculation functions or fields from multiple data sources'.
What am I missing?
Found one solution, using level of detail:
SQRT({ EXCLUDE [Name] : AVG([Residual_Squared])})