Plotting df Model with Two Covariables

[juan pablo Zurano]

Hi folks,

I have some problems plotting a distance model with two covariables.

My model is:

hr.size.amb <- ds(df_dist, key="hr", convert_units=conversion.factor, transect="line",  formula=~ size + amb)

`size` and `amb` are categorical variables with two and three levels, respectively.

After plotting the model like this:

 plot(size.amb, breaks=cutpoints, showpoints=TRUE)

  I would like to add level to level of the covariable size using:

add.df.covar.line(hr.size.amb, data=data.frame(size="small"), lwd=3, lty=1, col="#a50026")  

  I get the following error message:

Error in eval_with_covars(xx, data[i, ], df, pdf) : columns in `newdata` do not match those in fitted model

Could someone please help me with a simple example to make a plot with two covariables in the model?

Thanks so much, Juan

[Eric Rexstad]

Juan

Welcome to the list.

Because you have two covariates in your detection function model (`size` and amb​), you will likewise need values for both covariates in the data frame you are passing to add_df_covar_line​.  I don't know what value of amb​ you would like to examine, but here is a possibility

add_df_covar_line(hr.size.amb, data=data.frame(size="small", amb=mean(df_dist$amb, na.rm=TRUE)), lwd=3, lty=1, col="#a50026")  

This will show the shape of the fitted detection function when size​ is small and amb​ is the mean of the values of amb​ in your data set.

Alternatively, you could simply set the value of amb​ in your new data set to a value of interest to you.

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Sent: 24 May 2024 13:06
To: distance-sampling <distance...@googlegroups.com>
Subject: [distance-sampling] Plotting df Model with Two Covariables

 

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[juan pablo Zurano]

Dear Eric

Thank you very much for your answer. I have created a plot using both covariates as follows:  

plot(hr.size.amb, showpoints=T)

add_df_covar_line(hr.size.amb, data=data.frame(size="small", 

                                                                                   amb="grassland"), 

                                 lwd=3, lty=1, col="#bd0026")

Regards Juan

--

Juan Pablo Zurano

Instituto de Biología Subtropical (IBS, CONICET-UNaM), Nodo Iguazú

Av. Tres Fronteras 183 (3370) Puerto Iguazú, Misiones, Argentina.

Telefono: +54 3757 42-3289 Celular: +54 3764 15 879558, 

www.ibs-conicet.gob.ar

JPZ - Google Scholar