Merging worksheets

For data collection reasons, it may still be the case that data from essentially the same array are sourced from several different file, e.g. abundance of comparable species lists over a set of sites but with data from different years held in different Excel sheets. If those sites, or some of them, need to be analysed over the years then the best strategy is often to read all the different files into PRIMER and then Tools>Merge them to a common worksheet. Before entry, the sample labels should be unique, e.g. identify the year as well as the site and the replicate number etc, and species names (or numbers) be consistently spelt. Then runs of Merge will stitch the sheets together, a pair at a time, expanding the species lists accordingly to take account of the fact that different years may have species lists of slightly different composition, length or order, and zeros will be added in relevant cells (or Missing! if this is selected as more appropriate, e.g. as it would be for environmental data). Not all data for the same set of sample labels should necessarily go into a single worksheet, e.g. species abundances and environmental variables for the same set of sites/times are usually best kept in separate arrays because sample resemblance matrices (Section 5) will often need to use different coefficients. Whether environmental information is best held as a separate data array or as a factor sheet associated with a species array depends on the data type and context: factors are categorical (whether unordered or numerically ordered) whereas data arrays are numerical. Some variables may appear in both ways, e.g. water depth in an abiotic matrix and as a factor (shallow, mid, deep).