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Miscellaneous Functions for Working with 'stars' Rasters
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michaeldorman/starsExtra
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R packagestarsExtra provides several miscellaneous functions forworking withstars objects, mainly single-band rasters. Currentlyincludes functions for:
- Focal filtering
- Detrending of Digital Elevation Models
- Calculating flow length
- Calculating the Convergence Index
- Calculating topographic aspect and slope
CRAN version:
install.packages("starsExtra")GitHub version:
install.packages("remotes")remotes::install_github("michaeldorman/starsExtra")
Once installed, the library can be loaded as follows.
library(starsExtra)The complete documentation can be found athttps://michaeldorman.github.io/starsExtra/.
The following code applied a 15*15 mean focal filter on a 533*627stars Digital Elevation Model (DEM):
data(carmel)carmel_mean15= focal2(x=carmel,# Input 'stars' rasterw=matrix(1,15,15),# Weightsfun="mean",# Aggregation functionna.rm=TRUE,# 'NA' in neighborhood are removedmask=TRUE# Areas that were 'NA' in 'x' are masked from result)
The calculation takes: 0.5625446 secs.
The original DEM and the filtered DEM can be combined and plotted withthe following expressions:
r= c(carmel,carmel_mean15,along=3)r= st_set_dimensions(r,3,values= c("input","15*15 mean filter"))plot(r,breaks="equal",col= terrain.colors(10),key.pos=4)
The following code section compares the calculation time offocal2 inthe above example withraster::focal (both using C/C++) and thereference methodfocal2r (using R code only).
library(microbenchmark)library(starsExtra)library(raster)data(carmel)carmelr= as(carmel,"Raster")res= microbenchmark(focal2= focal2(carmel,w=matrix(1,15,15),fun="mean",na.rm=FALSE),focal= focal(carmelr,w=matrix(1,15,15),fun=mean,na.rm=FALSE),focal2r= focal2r(carmel,w=matrix(1,15,15),mean),times=10)res#> Unit: milliseconds#> expr min lq mean median uq max neval#> focal2 542.3506 546.0164 587.9224 554.3557 609.8761 793.5663 10#> focal 114.3561 115.9764 142.2213 119.7932 125.9327 339.7064 10#> focal2r 17236.5407 17367.5100 17734.2765 17634.1378 17902.5663 19048.0060 10
boxplot(res)
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Miscellaneous Functions for Working with 'stars' Rasters
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