Re: [unmarked] how to express psi, col, ext if no correlation with variables

[Marc Kery]

Dear James,

in exactly the same way as you would do it when fitting some linear model to normally-distributed data such as body mass, with R function lm().

"Non-correlation" = constant parameter = intercept-only model = '1' in the model formula.

Best regards  ---- Marc

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From: unma...@googlegroups.com <unma...@googlegroups.com> on behalf of James Shelley <jamessh...@gmail.com>
Sent: Tuesday, October 3, 2023 02:14
To: unmarked <unma...@googlegroups.com>
Subject: [unmarked] how to express psi, col, ext if no correlation with variables

 

Hi,

I have a question relating to a multi-year fish presence/absence dataset that I am fitting a dynamic occupancy model to. I'd like to see if the percentage of days where beneficial flows have occurred in each primary sampling period relate to changes in each species' occupancy dynamics. There is also a variable describing barriers to migration. I have used 'year' as a detection covariate. 

The best fit model to my data is one where occupancy is not correlated with any of my variables (see attached image), but colonisation and extinction are. I was wondering how I express a non-correlation in the model formula?

Thanks very much for your time. It's much appreciated.

Regards,

James

dynamic_occ_m1 <- colext(
  # Psi depends on initial Autumn flow conditions
  psiformula = ~?,
  # colonization depends on change in flow and barrier conditions
  gammaformula = ~springflow_time + summerflow_time + barrier_time,

  # extinction  depends on change in Autumn flow conditions
  epsilonformula = ~autumflow_time,
  # Detection varies with year
  pformula = ~year,
  data = Tupong_unmarkedMultFrame,

method = "BFGS",
  control=list(maxit=1000, trace=TRUE, REPORT=1))

Thanks in advance for your time. It's much appreciated.

Regards,

James

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