Publications by dylan
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 difference in elevation applied to an n-by-n window of cells: Equation 4 from (Park et al, 2001) whe...
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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 of this type of data can complicate standard analysis, summarization, and visualization. The aqp packag...
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Just for Fun: Using R to Create Targets
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 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 tutorials about learning R and...
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What would a 25th, 50th, and 75th percentile soil profile look like?
I have mentioned the AQP package in previous entries. One of the functions in this package generates aggregate soil profile data, from a collection of soil profiles that are related by some factor: common lithology, common landscape position, and so on. Typically the mean, or median (50th percentile) is used to generate a new aggregate profile, t...
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GRASS Can Make Pretty Maps
I have posted a couple examples in the past on the topic of high quality map production from GRASS GIS— usually via the Generic Mapping Tools. I am not sure why, but I have previously avoided using the traditional cartographic output module that is bundled with GRASS (ps.map). This is despite the fact that there is now an excellent collection o...
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Soil Properties Visualized on a 1km Grid
Fresno Area Urban Areas vs Irrigated LCC: grey regions are current urban areas A couple of maps generated from a 1km gridded soil property database, derived from SSURGO data where available with holes filled with STATSGO data. Soil properties visualized at this scale illustrate several important soil-forming factors operating within California: s...
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AQP Examples: Profile Visualization
Two examples of the output from the profile_plot() function, using data from the Sierra Foothill Region, CA. 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 tutorials about learning R and many other topics. Click he...
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More AQP (algorithms for quantitative pedology) Examples
The aqp package can be downloaded from R-Forge. 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 tutorials about learning R and many other topics. Click here if you're looking to post or find an R/data-science job. ...
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A Visualization of Soil Taxonomy Down to the Subgroup Level
It turns out that you can generate a quasi-numerical distance between soil profiles classified according to Soil Taxonomy (or any other hierarchical system) using Gower’s generalized dissimilarity metric. For example, taxonomic distances computed from subgroup membership are based on the number of matches at the order, suborder, greatgroup, and...
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Updated SoilWeb Usage Statistics
Google Earth Access Trends: Daily Requests 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 tutorials about learning R and many other topics. Click here if you're looking to post or find an R/data-science job. Want...
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