Transforming and adjusting your data

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5.3

Dealing with zeros

Rows or columns in the working data holding zero values can be removed. On the

Working Data page select Handling zeros in the Type of Adjustment panel.

Select the adjustment to be made and click on Submit to make the change.

The possible options are as follows.

Deselect Rows: Removes row not wanted in this analysis. This does not delete the

data, it only removes it from the working dataset

Deselect Columns:Removes column not wanted in this analysis. This does not delete

the data, it only removes it from the working dataset

Delete zero columns   Every column in the data set that only contains zeros is

removed.

Delete zero rows   Every row in the data set that only contains zeros is removed.

Remove sparse columns   Every column in the data set which contains < x non

zero elements is removed. The value of x is entered by the user in the At least x non

zero value text box.

Remove sparse rows   Every row in the data set which contains < x non zero

elements is removed. The value of x is entered by the user in the At least x non zero

value text box.

Beals   Beals smoothing is used on sparse data sets where many of the samples hold

a small proportion of the total species list. As the transformation only uses the

presence/absence of species, it should not be applied to good quality quantitative

data as you will be discarding much of your information. It should only be performed

on data arranged with the samples as columns. Described and discussed by Beals

(1984) and McCune (1994) respectively, each element, eij, in the data array is

replaced by:

where i is the column (sample) number, j is the row (species) number, Ni is the

number of species in column (sample) i, Bothjk is the number of samples holding both

species j and k, Samplesk is the number of samples holding species k and maxS is the

total number of columns (samples).

5.4

Transposing data

Use this option to switch the rows and columns of the data set. Like all the other

adjustments it is applied to the working data set. Select transpose in the Type of

Adjustment radio box and click on the Create working data button.

Copyright 2004  PISCES Conservation Ltd