Forum: open-discussion

RE: Comparing output from gdistance's costDistance() to other methods [ Reply ] By: Tabitha Graves on 2012-05-22 17:15	[forum:5707]
To compute correctly you need to calculate the transition function differently. It should be: tr1 <- transition(r, transitionFunction = function(x) 1/mean(x), directions=8) because working on conductance values rather than distance values. -Tab

RE: Comparing output from gdistance's costDistance() to other methods [ Reply ] By: Robby Marrotte on 2012-05-21 17:03	[forum:5706]
Alright, I'll try the Grass lcp function hopefully it confirms that either the Landscape ecology toolbox or the costDistance() is doing something wrong. I've been double checking of the sites are being processed in the same order and it seems that they have been. Thanks

RE: Comparing output from gdistance's costDistance() to other methods [ Reply ] By: Jacob van Etten on 2012-05-20 03:38	[forum:5701]
As the costDistance() example shows, I did some very simplistic comparisons with GRASS.

RE: Comparing output from gdistance's costDistance() to other methods [ Reply ]
By: Jacob van Etten on 2012-05-20 02:46

[forum:5700]

No, I haven't done any comparisons. I haven't given much priority to the distance functions, which I hardly use myself. However, before publishing an alpha version, I will do some more thorough checking.

I recently fixed a bug in resistanceDistance(). Also, there are differences between the CircuitScape and gdistance that I still need to explain in the docs.

I don't know why costDistance() gives different outputs from ArcGIS.

Comparing output from gdistance's costDistance() to other methods [ Reply ]
By: Robby Marrotte on 2012-05-19 18:34

[forum:5699]

Hello,

I was wondering if anybody has ever sat down and looked whether the output from costDistance() is similar to output from similar methods such as the least-cost path function in the Landscape genetics toolbox for ArcGIS?

I get very different results and I'm wondering if it's my input, but so far it doesn't seem like it. Also I noticed that the output from the resistance function in gdistance is also very different comapred to output from circuitscape.

Has anybody noticed this?

Thanks