Blog Archives

Potential Loss of Arable Land in the Central San Joaquin Valley, CA

August 17, 2009
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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...

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Computing Statistics from Poorly Formatted Data (plyr and reshape packages for R)

July 9, 2009
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  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...

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Using R to Create Misc. Patterns [smocking]

July 4, 2009
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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...

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Summarizing Grouped Data in R

July 3, 2009
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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

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Accessing Soil Survey Data via Web-Services

May 28, 2009
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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...

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Making Sense of Large Piles of Soils Information: Soil Taxonomy

May 27, 2009
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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...

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Simple Approach to Converting GRASS DB-backends

May 23, 2009
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  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...

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Interesting R Packages

April 27, 2009
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  CHNOSZ Chemical thermodynamics library and activity diagram software   read more

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