The SPEIbase was one of the most downloaded items of digital.CSIC in 2010 in various formats. The raw version of the data base was the second absolute item with 13021 downloads since March 2010, while the plain text version was third with 11626 downloads. The netCDF version ranked 13th with 4012 downloads. Digital.CSIC is the […]
Archivos del autor: sbegueria
Generating spatially correlated random fields with R
In several occasions I needed to generate synthetic data with a desired level of spatial autocorrelation. Here I will show how to generate as many such fields as we need by using R, an open-source port of the S language for statical analysis. I will concentrate on two alternative ways of generating spatially correlated random fields (commonly known as unconditional […]
Generalized Least Squares regression: regression models with spatial autocorrelation
This is the R code for performing Generalized Least Squares regression without (mod0) and with spatial autocorrelation (mod1), using the gls function in the library nlme: # first load the nlme library library(nlme) # read data (forest recovery after forest fire) # 30000 cells from satellite imagery datos — read.csv(‘variables.csv’, sep=’;’, head=T) # create matrices to […]
Towards the implementation of a vector data type in GIS
In contrast to scalars, which only have magnitude, vectors are geometrical objects defined by a magnitude and a direction. They play an important role in physics, since they can represent the forces acting on a body, velocities and accelerations, etc. In Geographic Information Science (GIS) analysis we are used to work with scalar fields, h(x,y), which are continuous […]
