Publications by dylan
Interesting R Packages
CHNOSZ Chemical thermodynamics library and activity diagram software 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...
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Simple Approach to Converting GRASS DB-backends
Premise: The current default database back-end used by the GRASS vector model is DBF (as of GRASS 6.5), however this is probably going to be changed (to SQLite) in GRASS 7. The DBF back-end works OK, however it tends to be very sensitive (i.e. breaks) when reserved words occur in column names or portions of a query. Complex UPDATE statements don�...
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Making Sense of Large Piles of Soils Information: Soil Taxonomy
Western Fresno Soil Hierarchy: partial view of the hierarchy within the US Soil Taxonomic system Soil Data Field and lab characterization of soil profile data result in the accumulation of a massive, multivariate and three-dimensional data set. Classification is one approach to making sense of a large collection of this type of data. US Soil Tax...
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Accessing Soil Survey Data via Web-Services
Soil Survey Data Online Querying of NRCS Soil Survey Data Sometimes you are only interested in soils data for a single map unit, component, or horizon. In these cases downloading the entire survey from Soil Data Mart is not worth the effort. An online query mechanism would suffice. The NRCS provides a form-based, interactive querying mechanism a...
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Summarizing Grouped Data in R
A colleague of mine recently asked about computing basic summary statistics from grouped data in R. These are a couple examples that I suggested. Additional documentation for the plyr package can be found here. 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 o...
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Using R to Create Misc. Patterns [smocking]
Pattern Chunk Premise My wife asked me to come up with some graph paper for creating smocking patterns. After a couple of minutes playing around with R-base graphics functions, it occurred to me that several functions in the sp package would simplify grid-based operations. Some example functions, along with a simple approach to generating “int...
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Computing Statistics from Poorly Formatted Data (plyr and reshape packages for R)
Premise I was recently asked to verify the coefficients of a linear model fit to sets of data, where each row of the input file was a “site” and each column contained the dependent variable through time (i.e. column 1 = time step 1, column 2 = time step 2, etc.). This format is cumbersome in that it cannot be directly fed into the R lm() func...
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Potential Loss of Arable Land in the Central San Joaquin Valley, CA
Rapid urban and sub-urban expansion in the San Joaquin Valley have resulted in the loss of millions of acres of prime farmland in the last 100 years. Approximately 11% of class 1 (irrigated) land and 7% of class 2 land have already been paved over in the Fresno-Madera region (first image below). Recent projections in the expansion of urban areas ...
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Aggregating SSURGO Data in R
Premise SSURGO is a digital, high-resolution (1:24,000), soil survey database produced by the USDA-NRCS. It is one of the largest and most complete spatial databases in the world; and is available for nearly the entire USA at no cost. These data are distributed as a combination of geographic and text data, representing soil map units and their as...
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New R-Forge Site for Quantitative Pedology
Just back from the annual meetings, and it looks like there is a significant interest in collaborative R coding of soils-related algorithms and visualization. A new R-forge site has been created to host Algorithms for Quantitative Pedology. Public release of the ‘soil’ package should be ready in a couple weeks. Soil Profile Dendrogram read mo...
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