More AQP (algorithms for quantitative pedology) Examples
The aqp package can be downloaded from R-Forge.
read more [Read more...]
Articles by dylan
AQP Examples: Profile Visualization
Two examples of the output from the profile_plot() function, using data from the Sierra Foothill Region, CA.
read more [Read more...]
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 visualize... [Read more...]
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 bu... [Read more...]
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... [Read more...]
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 [Read more...]
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...
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... [Read more...]
R’s Normal Distribution Functions: rnorm and pals
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... [Read more...]
Updated SoilWeb for the iPhone + Alpha Android Version
Major updates to the SoilWeb iPhone Application.
read more [Read more...]
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, ... [Read more...]
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 ...
Getting Parent Material Data out of SSURGO
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 ... [Read more...]
SQLite as an alternative to shapefiles, and some GPS fun in R
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 garmin -f /dev/... [Read more...]
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 welcomed.
read more
Converting Alpha-Shapes into SP Objects
Just read about a new R package called alphahull (paper) that sounds like it might be a good candidate for addressing this request regarding concave hulls. Below are some notes on computing alpha-shapes and alpha-hulls from spatial data and converting the results returned by ashape() and ahull() into SP-class objects. ...
Estimating Missing Data with aregImpute() {R}
Missing Data
Soil scientists routinely sample, characterize, and summarize patterns in soil properties in space, with depth, and through time. Invariably, some samples will be lost or sufficient funds required for complete characterization can run out. In these cases the scientist is left with a data table that contains holes (... [Read more...]
InfoChimps
This looks interesting: http://infochimps.org/search?query=soil
[Read more...]
Accessing Climate Change Data and a Custom Panel Function for Filled Polygons
GCS Model Grids
Recently finished some collaborative work with Vishal, related to visualizing climate change data for the SEI. This project was funded in part by the California Energy Commission, with additional technical support from the Google Earth Team. One of the final products was an interactive, multi-scale Google Earth ... [Read more...]
Yet Another plyr Example
another plyr example quantiles (0.05, 0.25, 0.5, 0.75, 0.95) of DSC by temperature bin
There are plenty of good examples on how to use functions from the plyr package. Here is one more, demonstrating how to use ddply with a custom function. Note that there are two places where the example function may blow up ...
Copyright © 2022 | MH Corporate basic by MH Themes