Publications by dylan

A Quick Demo of SoilProfileCollection Methods and Plotting Functions

04.01.2012

Here is a quick demo of some of the new functionality in AQP as of version 0.99-9.2. The demos below are based on soil profiles from an archive described in (Carre and Girard, 2002) available on the OSACA page. A condensed version of the collection is available as a SoilProfileCollection object in the AQP sample dataset “sp5“. AQP Sample Data...

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AQP Demo: Interfacing with PedonPC Databases using the ‘soilDB’ Package

12.01.2012

Here is a quick, draft demo on extracting soils data from a PedonPC database, and performing some common analysis with functions from AQP. The newly released soilDB package makes it possible to rapidly extract soils data from PedonPC, local NASIS, and SDA. Thanks to Jay Skovlin for his contributions to this package and his knowledge regarding the...

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AQP / soilDB Demo: Dueling Dendrograms

14.03.2012

Previously, soil profile comparison methods from the aqp package only took into account horizon-level attributes. As of last week the profile_compare() function can now accommodate horizon and site-level attributes. In other words, it is now possible to compute pair-wise dissimilarity between soil profiles using a combination of horizon-level pro...

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A Graphical Explanation of how to Interpret a Dendrogram

15.03.2012

Dendrograms are a convenient way of depicting pair-wise dissimilarity between objects, commonly associated with the topic of cluster analysis. This is a complex subject that is best left to experts and textbooks, so I won’t even attempt to cover it here. I have been frequently using dendrograms as part of my investigations into dissimilarity co...

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Dissimilarity Between Soil Profiles: A Closer Look

23.03.2012

Continuing the previous discussion of pair-wise dissimilarity between soil profiles, the following demonstration (code, comments, and figures) further elaborates on the method. A more in-depth discussion of this example will be included as a vignette within the 1.0 release of AQP. Profile Dissimilarity Demo: MVO Soils read more Related To leave...

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AQP Kick-Start

27.03.2012

A fun kick-starter for anyone interested in working with soil profile data in R, via AQP. See in-line comments for details. Up next, profile slicing and aggregation. read more Related To leave a comment for the author, please follow the link and comment on their blog: dylan's blog. R-bloggers.com offers daily e-mail updates about R news and t...

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R Quickie: Custom Panel Functions and Default Arguments

16.04.2012

Sometimes the basic functionality in lattice graphics isn’t enough. Custom “panel functions” are one approach to fully customizing the lattice graphics system. Two examples are given below illustrating how to define an (inline) custom panel function for adding a regression line to an entire data set in the presence of grouping variable. The...

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soilDB Demo: Processing SSURGO Attribute Data with SDA_query()

26.04.2012

Mapping near Paloma, CA This image has nothing to do with the following content. A quick example of how to use the USDA-NRCS soil data access query facility (SDA), via the soilDB package for R. The following code describes how to get component-level soils data for Yolo County (survey area CA113) from SDA and compute representative sub-order level...

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Extracting an image chunk from a collection of Large MrSid Images

04.06.2012

Recently needed to extract a small “chunk” from a collection of adjacent MrSid mosaics, each about 4Gb in size. Once again, GDAL came to the rescue, and saved much time and agony wile working with very large, compressed, and proprietary-format files. Two lessons learned: The GDAL VRT format can save a lot of time and effort by providing acce...

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Basic documentation for soilDB package (R) now available

29.08.2012

A proper introduction to the soilDB package is now available here. Installation and basic usage are covered. More detailed, task-specific documentation on aqp and soilDB will be available soon. read more Related To leave a comment for the author, please follow the link and comment on their blog: dylan's blog. R-bloggers.com offers daily e-mai...

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