PiscesLogoSmallerStill Non-Integer Data

Top  Previous  Next

 

The program has been designed to analyse counts of animal and plant abundance and therefore SDR requires all numbers in the data set to be either binary presence-absence data (i.e. 0 or 1), or positive integers; in opening a data set, the program will check the data and alert you to any non-standard numbers which would cause the program to fail. You can then edit the data set to correct these data points, either in the original spreadsheet program, if you used one, or using the Edit Open Dataset button.

 

There are cases where data are only available as individuals per unit area or volume, where the densities are expressed as real numbers. Diversity indices and ordering can be undertaken on these data. Simply convert the data to integers by multiplication and rounding in the spreadsheet while preparing the data set.

 

The richness estimators are not designed to be used on density data. For example, some methods need the number of species represented by one or two individuals in a sample. This cannot be obtained from numbers per unit area or similar measures. However, if you have a number of samples you can convert your data to presence/absence data and use the Chao presence-absence index. This index uses the number of species recorded in 1, 2 or more samples to estimate total species richness.