Sliding semilandmarks

[Bruno Ferreto Fiorillo]

I'm attempting to slide my semilandmarks, and I came across instructions suggesting that I organize them into a matrix format (see the example below where each number represents a landmark). However, this approach isn't feasible for me due to the complexity of my design and the large number of landmarks and semilandmarks involved. Is there a way to slide my semilandmarks without needing to specify the order in which landmarks and semilandmarks are arranged?

curveslide<-read.table("dadosmg/curves.slide.txt",h=T) curveslide<-as.matrix(curveslide) curveslide #> before slide after 
#> [1,] 2 14 15
#> [2,] 14 15 16 
#> [3,] 15 16 17
#> [4,] 3 17 16 

[Adams, Dean [EEOB]]

Bruno,

 

The short answer is no. The algorithm cannot determine which landmarks are fixed points and which points are semilandmarks without the user providing it some information about that. Without some sort of additional information, it is too much to expect the GPA to just know which landmarks the user intends to use as fixed points and which to use as sliders. That information is user- and dataset-specific.

 

For semilandmarks on surfaces, one just gives it a list of landmarks that are surface sliders (e.g.,. c(3,4,5,6,…)). That is easy to generate.

 

For semilandmarks on curves, one must create the slider matrix that you showed in your email. One can attempt to do this with the ‘define.sliders’ function, which allows you to click on the before, slider, after points to generate the matrix. Some users have found this function to be helpful (be sure to read the instructions!).

Dean

 

Dr. Dean C. Adams

Distinguished Professor of Evolutionary Biology

Department of Ecology, Evolution, and Organismal Biology

Iowa State University

https://faculty.sites.iastate.edu/dcadams/

phone: 515-294-3834

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[Bruno Ferreto Fiorillo]

Dear Dr. Adams,

Thank you again for all your patience and support.

It took me a few hours for organizing my dataset but it worked. I think I successfully slid my semilandmarks.

Best regards.