# An Overview of the aqp Package

Soil morphology, observed properties, and geomorphic context represent a complex package of interrelated information that can be difficult to analyze and communicate as a whole. Graphical methods such as soil profile sketches and cross-sections represent a few of the possible methods commonly used to report on these kind of data. The Algorithms for Quantitative Pedology (AQP) project encompasses several related R packages tailored to this style of work. A specialized data structure (SoilProfileCollection) maintains linkages between soil horizons, diagnostic features, above-ground data, and geomorphic context. SoilProfileCollection objects can be filtered, subset, resampled (over new depth intervals), and re-ordered; all while preserving links to above and below-ground, linked data. Functions are provided for the conversion of soil colors to and from Munsell notation and several other color space coordinates. Graphical methods for the SoilProfileCollection provide a simple but flexible framework for the design and layout of soil profile sketches, aligned to x and or y axes defined by linked data.

# Related Tutorials by Topic

## Soil Morphology

- Soil Profile Sketches
- Visualization of Horizon Boundaries
- Assigning Generalized Horizon Labels
- Dealing With Troublesome Data
- Simulation of Soil Morphology by Perturbation
- Soil Texture Visualization Ideas
- SPC Sketch Tips
- Vertical vs. Perpendicular Horizon Depths

## Soil Color

- Mixing Munsell Colors
- Soil Color Contrast
- Some ideas on summarizing soil color
- Soil Color Tiles
- Investigating Soil Color
- Some Ideas on Soil Color Signatures
- Soil Color Transition Probability

## Numerical Classification

- Pair-Wise Distances by Generalized Horizon Labels
- Pair-Wise Distance Between Profiles and Mixed Variable Types

## Soil Hydrology

- Theoretical Water Retention Curves
- Water Retention Curve Development from KSSL Data

## Geomorphology

- Hydrologic Ordering of Geomorphic Proportions
- Exploring Geomorphic Summaries

## Soil Taxonomy

- What does a subgroup look like?
- Querying Soil Series Data

## Multivariate Summaries of Soil Property Data

- L1 Profiles
- Getting and Comparing KSSL Data

## Soil Spectroscopy

- Soil Colors from VNIR Spectra

# Function Index by Topic

## SoilProfileCollection Objects

### Creation

- `depths()`: init an SPC from `data.frame`
- `site()`: set or add site-level attributes of an SPC
- `quickSPC()`: quickly build an SPC from simple text templates
- `random_profile()`: generate random SPC from suite of depth functions
- `rp()`: convenient wrapper of `random_profile()` for simulating large colections

### Metadata

- `hzdesgnname()`: get/set column containing horizon designations
- `hzDesgn()`: get vector of horizon designations
- `hztexclname()`: get/set column containing horizon texture class
- `metadata()`: get/set SPC metadata (list)
- `hzID()`: get vector of horizon IDs
- `hzidname()`: get/set column containing horizon IDs
- `horizonDepths()` get/set columns containing horizon top and bottom depths

### Properties

- `length()`: number of profiles in a SPC
- `nrow()`: number of horizons in a SPC
- `names()`: list of horizon and site names
- `siteNames()`: site-level column names
- `horizonNames()`: horizon-level column names

### Subset

- `glom()`: extract horizons based on overlap criteria defined by point or interval
- `trunc()`: truncate SPC to given depth interval
- `subset()`: subset profiles based on logical expressions
- `subsetHz()`: subset horizons based on logical expressions
- `[`: `data.frame`-like subsetting of profiles (i-index) and/or horizons (j-index)
- `[[`: access site or horizon-level columns by name
- `k-index expressions`: `.FIRST`, `.LAST`, `.HZID`, `.NHZ`, `.BOTTOM`, `.TOP`

### Depth

- `min()`: minimum bottom depth within a SPC
- `max()`: maximum bottom depth within a SPC
- `depthOf()`: generalized “depth to” based on REGEX matching
- `minDepthOf()`: special case of `depthOf()`
- `maxDepthOf()`: special case of `depthOf()`
- `getSoilDepthClass()`: estimate soil depth based on REGEX matching applied to horizon designation and associated depth class
- `aggregateSoilDepth()`: statistical estimation of soil depth (REGEX matching of horizon designation) within groups of profiles

### Utility

- `combine()`, `c()`: combine multiple SPCs into a single SPC
- `duplicate()`: duplicate profiles within a SPC
- `perturb()`: randomly adjust horizon thickness or depths to simulate from a template SPC
- `shuffle()`: randomly shuffle horizon data or entire horizons
- `warpHorizons()`: expand / contract horizon thickness
- `harmonize()`: create new profiles within a SPC based sets of related horizon-level data
- `hzAbove()`, `hzBelow()`: locate horizons above or below some criteria
- `unique()`: determine uniqueness among profiles of an SPC via MD5 hash
- `split()`: split SPC into list of SPCs based on grouping factor
- `site()`: get site data as `data.frame`
- `horizons()`: get horizon data as `data.frame`
- `replaceHorizons()`: replace horizon data
- `diagnostic_hz()`: get/set diagnostic features
- `restrictions()`: get/set restrictions
- `denormalize()`: convert site-level data into horizon-level data via replication
- `compositeSPC()`: downgrade an SPC to list of site and horizon-level data

### Iteration

- `profileApply()`: apply a function to each profile within an SPC (slow but simple interface)
- `summarizeSPC()`: perform group-wise summaries over profiles within an SPC
- `transform()`: modify a SPC using expressions that operation on site or horizon-level data

### Change of Support

- `dice()`: convert SPC to 1 depth-unit intervals by replication
- `slab()`: apply an aggregate function over groups within a “dice()-ed” SPC
- `spc2mpspline()`: interface to equal-area spline fitting from mpspline2 package
- `segment()`: generate segment labels for depth-weighted aggregation
- `L1_profiles()`: create representative profiles via multivariate median (L1 estimator)
- `slicedHSD()`: apply Tukey’s HSD over groups within a “dice()-ed” SPC

### Horizon Depth Logic

- `accumulateDepths()`: fix horizon depths when old-style O horizon notation has been used
- `fillHzGaps()`: fill topological gaps in horizon depth
- `repairMissingHzDepths()`: attempt fixing missing or duplicated horizon bottom depths
- `flagOverlappingHz()`: flag horizons with perfect overlap
- `checkHzDepthLogic()`: apply battery of horizon depth topological tests
- `splitLogicErrors()`: split an SPC according to variety of possibly horizon depth errors
- `HzDepthLogicSubset()`: remove profiles from an SPC if any depth logic errors are present

### Data QC

- `evalMissingData()`: report metrics of missing data by profile within SPC
- `missingDataGrid()`: visual indication of missing data
- `profileInformationIndex()`: experimental indices of “information content” by profile

### Object Coercion

- `as(SPC, 'list')`: convert SPC to `list`
- `as(SPC, 'data.frame')`: convert site and horizon data to `data.frame`
- `as(SPC, 'sf')`: convert site and spatial data to sf object

### Spatial Data

- `prj()`: get/set coordinate reference system (CRS) metadata
- `initSpatial()`: set (site-level) column names containing coordinates
- `getSpatial()`: get spatial data (site + coordinates) from an SPC

### Internal Consistency

- `checkSPC()`: check SPC for internal consistency
- `rebuildSPC()`: re-make an SPC from a previous version of aqp (rarely required)

## Soil Profile Sketches

- `plotSPC()`: create sketches of soil profiles from an SPC
- `explainPlotSPC()`: explain various elements of a soil profile sketch
- `groupedProfilePlot()`: create grouped sketches of soil profiles
- `plotProfileDendrogram()`: “hang” profile sketches from a dendrogram
- `plotMultipleSPC()`: create sketches from multiple, possibly non-conformal SPCs
- `addBracket()`: add vertical brackets beside soil profile sketches
- `addDiagnosticBracket()`: add vertical brackets beside soil profile sketches based on diagnostic features
- `addVolumeFraction()`: add visual explanation of coarse fragment volume to soil profile sketches
- `alignTransect()`: align soil profiles to an external gradient such as topographic sequence

## Soil Color / Color Science

### Color Conversion

- `col2Munsell()`: convert various color notations to Munsell notation
- `munsell2rgb()`: convert Munsell notation to sRGB or CIELAB color coordinates
- `parseMunsell()`: parse and optionally convert a munsell color
- `spec2Munsell()`: estimate the closest Munsell color given reflectance spectra in the visible range
- `getClosestMunsellChip()`: estimate a reasonably close Munsell color given non-standard notation
- `estimateSoilColor()`: estimate moist soil color from dry soil color (and vice versa)

### Comparison

- `colorContrast()`: pair-wise color contrast and CIE2000 (dE00) based on colors in Munsell notation
- `colorContrastPlot()`: visual explanation of soil color contrast and dE00
- `contrastChart()`: Munsell color book style explanation of soil color contrast and dE00
- `soilColorSignature()`: derive soil color signatures for profiles within an SPC

### Aggregation

- `colorChart()`: Munsell color book representation of color frequency
- `colorVariation()`: describe color variation using dE00 (based on average human color perception)
- `aggregateColor()`: estimate color proportions within an SPC according within groups of horizons
- `aggregateColorPlot()`: graphical explanation of output from `aggregateColor()`
- `colorQuantiles()`: marginal and L1 quantiles of color in CIELAB coordinates

### Utility

- `huePosition()`: generate an ordered factor of the standard Munsell hues
- `huePositionCircle()`: graphical representation of the standard Munsell hues, with optional simulation of common color vision deficiency
- `simulateColor()`: simulate a range of Munsell colors given measures of central tendency and spread
- `previewColors()`: graphical preview of colors as a grid or via nMDS
- `soilPalette()`: generate swatch-like arrangements of colors and labels
- `equivalentMunsellChips()`: for a specified Munsell color, identify other Munsell colors with a very lower CIE2000 color contrast difference

### Simulation of Mixtures

- `mixMunsell()`: simulate an subtractive mixture of pigments specified in Munsell notation
- `plotColorMixture()`: simulate a subtractive mixture of pigments, display reflectance spectra

## Numerical Classification of Soil Profiles

- `NCSP()`: numerical classification of soil profiles, within a `SoilProfileCollection`
- `compareSites()`: pair-wise comparison of site-level data from a `SoilProfileCollection`

## Pedology

- `allocate()`: perform one of several classification systems to soil property data
- `estimateAWC()`: estimate plant-available water holding capacity
- `correctAWC()`: apply rock fragment or soluble salt corrections to AWC estimates
- `hzDistinctnessCodeToOffset()`: convert horizon boundary distinctness codes to vertical offset
- `hzTopographyCodeToLineType()`: convert horizon boundary topography codes to line types
- `hzTopographyCodeToOffset()`: convert horizon boundary topography codes to offset
- `ph_to_rxnclass()`: convert pH to reaction class
- `rxnclass_to_ph()`: convert reaction class to pH range
- `ReactionClassLevels()`: ordered factor of reaction classes
- `horizonColorIndices()`: compute various soil color-based indices to horizons within an SPC

### Soil Texture

- `textureTriangleSummary()`: graphical summary of sand, silt, clay fractions on a soil texture triangle
- `bootstrapSoilTexture()`: simulation of realistic compositions (sand, silt, clay) from a small set of example data
- `SoilTextureLevels()`: ordered factor of soil texture classes
- `texcl_to_ssc()`: convert soil texture classes to sand, silt, clay centroids
- `ssc_to_texcl()`: convert sand, silt, clay values to soil texture class
- `texture_to_taxpartsize()`: convert soil texture to Soil Taxonomy particle size class

### Coarse Fragments

- `fragmentSieve()`: classify coarse fragments by fragment diameter
- `texmod_to_fragvoltot()`: estimate ranges in coarse fragment volume based on a soil texture modifier
- `texture_to_texmod()`
- `fragvol_to_texmod()`
- `fragmentClasses()`: coarse fragment diameter thresholds used by USDA-NRCS

### Soil Taxonomy

- `getArgillicBounds()`: estimate the upper and lower boundaries of an argillic horizon
- `getCambicBounds()`: estimate the upper and lower boundaries of a cambic horizon
- `getSurfaceHorizonDepth()`
- `getMineralSoilSurfaceDepth()`
- `getPlowLayerDepth()`
- `hasDarkColors()`
- `estimatePSCS()`

### Generalized Horizon Labels (GHL)

- `generalize.hz()`: apply REGEX rules to group horizon designations into a reduced set of “generalized horizon labels”
- `evalGenHZ()`: evaluate internal consistency of assigned GHL
- `genhzTableToAdjMat()`: convert a cross-tabulation of GHL vs. original horizon designations to adjacency matrix
- `get.ml.hz()`: extract most likely horizon boundary depths from probability depth functions
- `guessGenHzLevels()`: estimate the correct ordering of GHL given horizon depths
- `GHL()`: get/set GHL metadata for a `SoilProfileCollection`

## Misc.

- `invertLabelColor()`: automatic adjustment of label color for maximum contrast, based on specified background color
- `hzTransitionProbabilities()`: derive transition probability matrix from horizon level data
- `mostLikelyHzSequence()`: use Markov Chains to predict the most likely sequence of horizons

### Accuracy and Uncertainty

- `shannonEntropy()`: Shannon entropy
- `brierScore()`: Brier’s score
- `tauW()`: weighted tau statistic

### Overlapping Annotation

- `findOverlap()`: identify overlap within a vector of positions based on a given threshold
- `overlapMetrics()`: metrics of overlap within a vector or positions based on a given threshold
- `fixOverlap()`: attempt the minimum of adjustments to vector of positions such that a given distance threshold is enforced

## Example Data

- `sp1`
- `sp2`
- `sp3`
- `sp4`
- `sp5`
- `sp6`
- `sierraTransect`
- `wilson2022`
- `rowley2019`
- `jacobs2000`
- `osd`
- `SPC.with.overlap`
- `us.state.soils`
- `soil_minerals`
- `munsell`
- `equivalent_munsell`
- `munsellHuePosition`
- `munsell.spectra`
- `spectral.reference`
- `ROSETTA.centroids`
- `reactionclass`
- `soiltexture`