Examples for reclassify raster in r how to#
Examples for reclassify raster in r full#
Examples for reclassify raster in r code#

Note that this is a different function from the deprecated overlay function in the sp package. The function overlay can be used to do the raster math and create the new raster. # Elevation rasterĮlevpath 200 and the landcover type is Evergreen Needleleaf Forest or Evergreen Broadleaf Forest (land cover values 1,2). The QGIS sample data has an elevation raster that we will read. We already have land cover so let’s read in elevation. In this example we will identify forest areas with elevations above 200 meters using two input rasters.

Examples for reclassify raster in r how to#

Create a RasterBrick and do raster mathĪs a final step/example we will use the sample data from QGIS to demonstrate how to create a new raster using raster math (similar to raster calculator in ArcGIS). Title='Compare R Raster Package Extract ArcGIS Tabulate Area')Įssentially the same results from the two methods. Labs(x='R Raster Package Extract', y='ArcGIS Tabulate Area', Ggplot(both, aes(Freq, Freq_GIS))+geom_point(size=4,alpha=0.5, color='purple4')+ we need to divide by the number of feet in a # the area is in square feet - to convert to 'Cells' which Mutate(Freq=ifelse(is.na(Freq), 0, Freq))

Examples for reclassify raster in r full#

# type occur so with a full join you get 0 for Arc and NA for R. # in a region while in the raster packages no cells of this # note that arcgis returns 0 for land uses that do not occur # read in our tableĪrcgis%gather(key=Var1, value=area, -NAME_2)%>%

Now read in our results from ArcGIS and do some reformating.

Examples for reclassify raster in r code#

We don't want to leave the comforts of R so here we will create a python script from within R (using the cat function) and then we will run it with the system function.īy the way, if someone wants to submit the code for doing this in QGIS, I will add it here with attribution. In order to follow along on your own computer you need to have ArcGIS installed and Python needs to be accessible on the command line. Since most of us started doing these kinds of calculations in ArcGIS it may be comforting to see the R results side-by-side with those from ArcGIS – in particular the tabulate area tool. Compare with ArcGIS's Tabulate Area tool results We can see that the Anchorage region is the only one with urban land cover (though very little of it) and, as you can see in the maps, the North Slope has the highest percentage of shrubland and Yukon-Koyukuk has the most green area. Spread(key=Var1, value=percent.area, fill=0) # make wide format Percent.area=round(100*Freq/totcells,2)) %>% #cells by landuse/total cellsĭplyr::select(-c(Freq, totcells)) %>% # there is a select func in raster so need to specify Mutate(totcells=sum(Freq), # how many cells overall You could alternatively do this with the tempdir function. In our example, we are putting the data in a temporary folder which we’ve hard coded.

Careful, the size of the zipped file is approximately 21 Mbs. The data includes two raster datasets as well as multiple vector datasets. QGIS has a useful selection of sample data on their website. Library(gridExtra) # to arrange grid plots Be sure to load tidyr before raster, otherwise the extract tool from the raster library will be masked. If you're unfamiliar with dplyr and tidyr, which we use for data processing, you can check out our previous post on the topic. This post also makes extensive use of the “new” R workflow with the packages dplyr, magrittr, tidyr and ggplot2. In this post we show some simple (and not-so-simple) examples of how to work with raster data in R with a focus on the raster package. This means, of course, that more and more of your spatial-related workflow can be conducted without leaving R. In a previous post, for example, we showed that the number of spatial-related packages has increased to 131 since the first R release.

The amount of spatial analysis functionality in R has increased dramatically since the first release of R.