Data management

A few records, such as the record for day 197 for cow 24, have been removed (see Audit worksheet in CS6Data1). There was only one record for the two cows 549 and 807 during the first 7 weeks of lactation. As this period is crucial both to the study and to the analysis, we have decided to ignore these two cows.

An arbitrary decision was also made to remove records from a few cows with particularly long lactations. Measurements greater than 270 days of lactation have been ignored. An unusually high concentrate value of 16.1 kg fed to cow 801 on day 206 of lactation has also been deleted. This is probably a mistake in data entry.

When modifications are being made to a data set, many of an arbitrary nature, it is important, as done here, to make notes of the changes, so that someone else can see what was done and repeat the analysis in a different way, if necessary.

After reloading the 'edited' worksheet of CS6Data1 we find that GenStat has changed the dates into numerical formats. We can change the values back into dates using Spread → Column →Attributes/Format… and click 'cdate' and repeat for 'date'.