Sampling Occasion Limit?

questions concerning analysis/theory using program PRESENCE

Sampling Occasion Limit?

Postby David Steen » Fri Nov 07, 2008 1:35 pm

I have a presence/absence matrix with 21 sampling occasions. Although I am able to input the data in Presence 2.2, it saves only 15. Any leads on this discrepancy are appreciated.
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Postby darryl » Sun Nov 09, 2008 5:46 pm

Have you checked that the number of columns and number of occasions per season are correctly specified in the input data form? I've saved up to 300 occasion before with no problems.
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Postby David Steen » Sun Nov 09, 2008 8:54 pm

I can manually type in the appropriate number of rows and columns, but when I close the input data form and select the file from the "Enter Specifications for PRESENCE analysis" only 15 rows are included.
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Postby darryl » Sun Nov 09, 2008 9:48 pm

How recently have you downloaded PRESENCE? You may have gotten a build with a bit of a bug in it. The important thing here isn't the version number (it only indicates big changes), but the build number. Look for a number in the 'about' window (from help menu) like <08XXXX.XXXX>.

Otherwise, it's likely that you must be doing something that Jim hasn't expected because I don't recall anyone else having reported this error before.

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Postby David Steen » Mon Nov 10, 2008 12:31 pm

I'm using version 2.2 <080907.1133>

I have 86 sites and 21 sampling occasions.

There are some missing observations, as sites were sampled a minimum of 15 times and a max. of 21 times.

Perhaps there's a problem recognizing the missing observations?

Thanks,
Dave
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Postby darryl » Mon Nov 10, 2008 1:22 pm

Are you indicating them with either a "-" or a "." like it says in the help file?
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sampling occasion limit

Postby jhines » Mon Nov 10, 2008 5:22 pm

PRESENCE will stop reading input on a line when it encounters the end of the line, or a blank field. Missing values are input using '-' (without quotes). If your first record has a missing value at survey 16 and you used a blank character for missing, then PRESENCE will only save the first 15 surveys.
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Postby David Steen » Mon Nov 10, 2008 5:26 pm

I don't see that information in the help file, but I've clearly made that mistake.

Thank you.
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