Update r.vif add-on for GRASS GIS

I just updated the r.vif add-on. The add-on let’s you do a step-wise variance inflation factor (VIF) procedure. As explained in more detail here, the VIF  can be used to detect multicollinearity in a set of explanatory variables. The step-wise selection procedure provides a way to select a et of variables with sufficient low multicollinearity.

The update should make the computation of VIF much faster. For very large raster layers it is possible to have the VIF computed based on a random subset of raster cells. There is also a low-memory option. This allows one to run this add-on with much larger data sets. But, as explained in the r.vif manual page, it also runs considerably slower.

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Update of r.forestfrag addon

I just updated the r.forestfrag addon for GRASS GIS. The addon, which I described before, was developed based on an script by Sylla consult,  and can be used to characterizes the degree of fragmentation following the approach proposed by Riiters et al. (2000). It identifies six categories of fragmentation, viz., interior, perforated, edge, transitional, patch, and undetermined, based on the amount of forest and its occurrence as adjacent forest pixels within a user-defined distance (i.e., the user sets the size of moving window used to compute the index).  Continue reading “Update of r.forestfrag addon”

Update to Ubuntu Preise Pangolin

Just though I share some first impressions about my upgrade to Ubuntu 12.04 (Precise Pangolin). The upgrade process itself wasn’t the best experience ever unfortunately. After the upgrade, I couldn’t even start up anymore. As it turns out, during the update process my GRUB bootloader got corrupted. After a bit of searching, I found an easy solution: the Boot-Repair disc. Simply download the ISO and burn it on CD (yes, you do need access to another computer). After booting my computer using the CD, Boot-Repair let me fix the issues with a simple click.

Having that out of the way, I could finally have a look at the changes.  Continue reading “Update to Ubuntu Preise Pangolin”