Testing age effect on capture probability in E-SURGE

questions concerning analysis/theory using programs M-SURGE, E-SURGE and U-CARE

Testing age effect on capture probability in E-SURGE

Postby Julia Geraci » Mon Jul 06, 2009 12:20 pm

Hello,
I would like to investigate the age effect on recapture probability in E-SURGE. To do so, I want to test logarithmic or quadratic age effects. How should I write it in GEMACO? If I need to create covariate files, how should I inser it in my model?
Many thanks for your answer

Julia
Julia Geraci
 
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Postby CHOQUET » Tue Jul 07, 2009 3:08 am

Hello,

First select the number of age classes A that you need in DATA STATUS
The sentence in GEMACO is by default for capture:

firste+nexte

In most of the case firste is the first capture rate which should be fixed
to one. nexte modelize age for the recapture rate. For a quadratic effect then use the following sentence:

firste+nexte(1:A).[i+nexte*x(1)+nexte*x(2)]

where x(1) is the vector of covariates for a linear trend with age and
x(2) is the vector of covariates for a quadratic trend with age.

x(1) and x(2) must be defined in an external file with the following format
with A=4 (see the manual p 35)

2
4 4
1 2 3 4
1 4 9 16

Note that for large values of A, it is better to standardized covariates.
One you have defined this file, select the menu "file of external covariates"
in GEMACO interface.

Sincerely,

Rémi
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