Blog Archives

Just for Fun: Using R to Create Targets

August 10, 2010
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OK, not really science or soil-related, but a fun 5 minute use of R to make something you can use to improve your hand-eye coordination. read more

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New R Package ‘aqp’: Algorithms for Quantitative Pedology [updates]

August 9, 2010
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New R Package ‘aqp’: Algorithms for Quantitative Pedology [updates]

  Soils are routinely sampled and characterized according to genetic horizons (layers), resulting in data that are associated with principal dimensions: location (x,y), depth (z), and property space (p). The high dimensionality and grouped nature...

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Using R and r.mapcalc (GRASS) to Estimate Mean Topographic Curvature

August 3, 2010
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Using R and r.mapcalc (GRASS) to Estimate Mean Topographic Curvature

Recently I was re-reading a paper on predictive soil mapping (Park et al, 2001), and considered testing one of their proposed terrain attributes in GRASS. The attribute, originally described by Blaszczynski (1997), is the distance-weighted mean differe...

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R’s Normal Distribution Functions: rnorm and pals

July 14, 2010
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The rnorm() function in R is a convenient way to simulate values from the normal distribution, characterized by a given mean and standard deviation. I hadn't previously used the associated commands dnorm() (normal density function), pnorm() (cumulative...

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Updated SoilWeb for the iPhone + Alpha Android Version

June 15, 2010
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Major updates to the SoilWeb iPhone Application. read more

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PostGIS in Action Book Review

June 8, 2010
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PostGIS in Action Book Review

I was recently asked to review a soon to be published book on PostGIS, a spatial extension to the very popular Postgresql relational database. I was very excited about receiving an early copy of this book, as the authors have provided countless tips, ...

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An XML Representation of the Keys to Soil Taxonomy?

May 28, 2010
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An XML Representation of the Keys to Soil Taxonomy?

Western Fresno Soil Hierarchy: partial view of the hierarchy within the US Soil Taxonomic system Maybe this is just craziness, but wouldn't be neat to have an XML formatted version of the Keys to Soil Taxonomy? The format might look something like the ...

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Getting Parent Material Data out of SSURGO

May 27, 2010
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  Parent material data is stored within the copm and copmgrp tables. The copm table can be linked to the copmgrp table via the 'copmgrpkey' field, and the copmgrp table can be linked to the component table via the 'cokey' field. The following queries illustrate these table relationships, and show one possible strategy for extracting the parent material information...

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SQLite as an alternative to shapefiles, and some GPS fun in R

May 24, 2010
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Finally made it out to Folsom Lake for a fine day of sailing and GPS track collecting. Once I was back in the lab, I downloaded the track data with gpsbabel, and was ready to import the data into GRASS. # import GPX from GPS: gpsbabel -t -i...

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Annotating Lattice Box and Whisker Plots

April 28, 2010
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Annotating Lattice Box and Whisker Plots

bwplot annotation example Sometimes you want to add a little text to box and whisker plots produced by the lattice function bwplot(). Here is one approach. Could be optimized a bit more to reduce manual specification of some elements. Suggestions...

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