Missing values in the Response

Dropping records with missing response

Unless a multivariate model is being fitted or missing values are being estimated, ASReml discards records with a missing response variable as the data is being read. The data file is not read until the linear model line has been parsed and the response variable identified.

Warning: Consequently, the data summary and any tabulation is based on those records where the response is not missing.

Estimating the missing values

It is sometimes computationally convenient to estimate missing values, for example, in spatial analysis of regular arrays, see example below. This is done by including mv in the fixed model. Formally, mv creates a factor with a covariate for each missing value. The covariates are coded 0 except in the record where the particular missing value occurs, where it is coded -1.

Missing values in multivariate analysis

In multivariate analyses, the R matrix is modified to reflect the missing value pattern.


NIN Alliance Trial 1989 variety ... row 22 column 11 !skip 1 ~ mu variety !r repl !f mv <1>2 <11>column AR1 .424 <22>row AR1 .904

See Also