3. When a data file is opened, all the data are dumped into the first cell,
rather than opening in the grid properly
This is usually because there are one or more blank cells in the second row of
data. If the blanks are replaced by zeros, or another row with no blanks is put in
the second position, the problem should disappear. Row 2 is the crucial one;
blank cells are tolerated elsewhere.
4. I entered the data in a spreadsheet program, and saved it as a csv file.
When I try to open it in CAP, the numbers are separated by ; not , so the
analysis will not run.
This is because some non British systems use ; instead of , to separate values in
a csv file. Open Windows Explorer, and change the file extension from csv to txt
(i.e. Filename.csv becomes Filename.txt). Open the txt file in Word or another
word processing program. Use the Find/Replace function to replace every ; with a
, then save the file again. Change the txt file extension back to csv. It should now
open and run perfectly in CAP.
5. I attempted to run Twinspan using the default settings but got an I/0 error
If you have large numbers in your data set this may occur. The reason is that, as
part of its normal operation, TWINSPAN adds some very large numbers to each
data value, in order to increase the discrimination between them. If you already
have large numbers the resulting values may be too large for the data types used
within the program. The solution is to transform your data. Usually a square root
transformation will resolve the matter.
6. In TWINSPAN OUT: concerning the list of Indicators and their sign (i.e.
Species 1 (+), Species 2 ( )), does the (+) represent species present in the
class and ( ) represent species NOT present in the class? If so, then are the
only sample points (quadrats) representing the TWINSPAN classes those
listed under the positive group?
In the TWINSPAN output Species1 (+) indicates that species1 is characteristic of
the quadrates classified to the right of the centroid of the primary axis of the
ordination. It does not mean that the Species1 is absent in all the quadrates to
the left of the centroid. An output of, say, Species2 ( ) would mean that Species2
is characteristic of quadrates to the left of the centroid. Remember that if
TWINSPAN is not undertaken on presence/absence data it uses pseudospecies
so the same species can be an indicator at different levels of abundance.
In the case of presence/absence data there will certainly be a strong tendency for
a positive species only to be present in the group of quadrates to the right.
However, this is not necessarily always the case.
7. Invalid floating point operation
Copyright 2004, PISCES CONSERVATION LTD