Blog Archives

Extract values from numerous rasters in less time

May 7, 2015
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These days I was working with a Shiny app for which the computation time is a big problem.Basically this app takes some coordinates, extract values from 1036 rasters for these coordinates and make some computations.  As far as I can (and please correct me if I'm wrong!) tell there are two ways of doing this task:1) load all the...

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Downloading and Visualizing Seismic Events from USGS

April 28, 2015
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Downloading and Visualizing Seismic Events from USGS

The unlucky events that took place in Nepal have flooded the web with visualization of the earthquakes from USGS. They normally visualize earthquakes with a colour scale that depends on the age of the event and a marker size that depends on magnitude. I remembered that some time ago I tested ways for downloading and visualizing data from USG...

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Accessing, cleaning and plotting NOAA Temperature Data

December 11, 2014
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Accessing, cleaning and plotting NOAA Temperature Data

In my previous post I said that my students are using data from NOAA for their research.NOAA in fact provides daily averages of several environmental parameters for thousands of weather stations scattered across the globe, completely free. In details, NOAA provides the following data: Mean temperature for the day in degrees Fahrenheit to tenths Mean dew point for the...

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World Point Grid

December 10, 2014
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These days I am following a couple of master projects dealing with renewable energy potentials at the global scale. We wanted to try and compute these potential using only free data and see how far we could go.For wind speed there are plenty of resourc...

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R Object-oriented Programming – Book Review

November 28, 2014
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R Object-oriented Programming – Book Review

(This article was first published on R Video tutorial for Spatial Statistics, and kindly contributed to R-bloggers) I have been asked to review the book “R Object-oriented Programming” by Kelly Black, edited by Packt publishing (£14.45 for the E-Book, £27.99 for Print+E-Book). The scope of the book is “to provide a resource for programming using the R language” and...

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Changing the Light Azimuth in Shaded Relief Representation by Clustering Aspect

September 24, 2014
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Some time ago I published an article on "The Cartographic Journal" regarding a method to automatically change the light azimuth in shaded relief representations.This method was based on clustering the aspect derivative of the DTM. The method was develo...

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Transform point shapefile to SpatStat object

August 19, 2014
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Today I wanted to do some point pattern analysis in R using the fantastic package spatstat.The problem was that I only had a point shapefile, so I googled a way to transform a shapefile into a ppp object (which is the point pattern object used by spats...

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Extract Coordinates and Other Data from KML in R

June 11, 2014
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KML files are used to visualize geographical data in Google Earth. These files are written in XML and allow to visualize places and to attach additional data in HTML format.In these days I am working with the MIDAS database of wind measuring stations a...

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Merge .ASC grids with R

April 2, 2014
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Merge .ASC grids with R

A couple of years ago I found online a script to merge several .asc grids into a single file in R.I do not remember where I found it but if you have the same problem, the script is the following: setwd("c:/temp") library(rgdal) library(raster) # ...

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Plotting an Odd number of plots in single image

March 3, 2014
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Plotting an Odd number of plots in single image

Sometimes I have the need to reduce the number of images for a presentation or an article. A good way of doing it is putting multiple plot on the same tif or jpg file.R has multiple functions to achieve this objective and a nice tutorial for this topic...

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