Blog Archives

Converting Alpha-Shapes into SP Objects

April 19, 2010
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Converting Alpha-Shapes into SP Objects

Just read about a new R package called alphahull (paper) that sounds like it might be a good candidate for addressing this request regarding concave hulls. Below are some notes on computing alpha-shapes and alpha-hulls from spatial data and converting the results returned by ashape() and ahull() into SP-class objects. Note that the functions...

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Estimating Missing Data with aregImpute() {R}

April 19, 2010
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  Missing Data Soil scientists routinely sample, characterize, and summarize patterns in soil properties in space, with depth, and through time. Invariably, some samples will be lost or sufficient funds required for complete characterization can run out. In these cases the scientist is left with a data table that contains holes (so to speak) in the rows/columns that are...

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InfoChimps

March 7, 2010
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InfoChimps

This looks interesting: http://infochimps.org/search?query=soil

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Accessing Climate Change Data and a Custom Panel Function for Filled Polygons

March 4, 2010
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Accessing Climate Change Data and a Custom Panel Function for Filled Polygons

GCS Model Grids Recently finished some collaborative work with Vishal, related to visualizing climate change data for the SEI. This project was funded in part by the California Energy Commission, with additional technical support from the Google Earth Team. One of the final products was an...

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Yet Another plyr Example

March 4, 2010
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Yet Another plyr Example

another plyr example quantiles (0.05, 0.25, 0.5, 0.75, 0.95) of DSC by temperature bin There are plenty of good examples on how to use functions from the plyr package. Here is one more, demonstrating how to use ddply with a custom function. Note that there...

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SoilWeb iPhone App: Beta-Testers?

February 23, 2010
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SoilWeb iPhone App: Beta-Testers?

iPhone App Screenshot rev 0.2 - icon iphone App Screenshot rev 0.2 - in Fresno   More Updates: The application is now...

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Numerical Integration/Differentiation in R: FTIR Spectra

February 23, 2010
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Numerical Integration/Differentiation in R: FTIR Spectra

  Stumbled upon an excellent example of how to perform numerical integration in R. Below is an example of piece-wise linear and spline fits to FTIR data, and the resulting computed area under the curve. With a high density of points, it seems like the linear approximation is most efficient and sufficiently accurate. With very large...

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Visual Interpretation of Principal Coordinates (of) Neighbor Matrices (PCNM)

February 21, 2010
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Principal Coordinates (of) Neighbor Matrices (PCNM) is an interesting algorithm, developed by P. Borcard and P. Legendre at the University of Montreal, for the multi-scale analysis of spatial structure. This algorithm is typically applied to a distance matrix, computed from the coordinates where some environmental data were collected. The resulting "PCNM vectors" are commonly used to describe...

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Two New Soils-Related KMZ Demos

February 10, 2010
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Two New Soils-Related KMZ Demos

LCC KMZ Soil Texture KMZ   Forgot to post these KMZ files: 1-km scale, aggregate LCC and soil texture data, derived from SSURGO. These are part of a series of KMZ / raster...

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Updates to SoilWeb

January 17, 2010
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Updates to SoilWeb

Soil Profiles in Color Added color support to the mini-profiles used in graphical map unit summaries, the Google Earth interface, and iPhone application. SSURGO doesn't contain soil color data, so colors (in Munsell notation) were extracted from the OSD database, and...

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