How to define my own background points (pseudo absence) with SWD or ASCII

[Madan K. Suwal]

Dear all, 

I want to define my own background points or pseudo absences in Maxent so that the same pseudo absences can be used in other models like Random Forest. 

it is because, I need them for post processing. 

they can be with SWD or ASCII.

but I don't see that option. 

any idea is appreciated. 

thanking you. 

[Jamie M. Kass]

Please consider working in R instead. This way, you can easily generate your own background points with randomPoints() from the "raster" package, then get their predictor variable values with extract(). If you don't want to work in R, you can also generate your own random points in ArcGIS with the Create Random Points tool, then get their values with Extract Values to Points, or one of other similar tools. I hope this answers your question.

Jamie Kass
PhD Student
City College, NYC

[Madan K. Suwal]

Thanks Jamie, 

I have that random points or background points, 

I want to define then as background point in MaxEnt (where by default MaxEnt create its own background points) 

or I am looking for an option to extract the background points generated by MaxEnt 

thanks

[Alyson Webber]

Perhaps turn those points into pixels that are of the same geo-reference as the parameter asciis, use it as a mask in the bias file, and set the number of background points to be the same as the number of pixels in your bias file? It probably would double select some and not select others, so I don't know if that would work.

[Jamie M. Kass]

I'm not sure about that technique, but for what you want to do (generate the background points yourself and input them directly into Maxent, then have them afterward to do something else with), R is the cleanest way to work. If you want to stick with the Maxent GUI, generate random points in ArcGIS or QGIS, extract the coordinates from the attribute table, and put them into a SWD file for input to Maxent. This way, Maxent will use your background points. Does this answer the question?

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Jamie Kass
PhD Student, Department of Biology
City College of New York, CUNY Graduate Center