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spMC (version 0.3.15)

transiogram: Empirical Transition Probabilities Estimation for 1-D MC

Description

The function estimates transition probabilities matrices for a \(1\)-D continuous lag spatial Markov chain.

Usage

transiogram(data, coords, direction, max.dist = Inf, 
            mpoints = 20, tolerance = pi / 8, reverse = FALSE)

Value

An object of the class transiogram is returned. The function print.transiogram is used to print computed probabilities. The object is a list with the following components:

Tmat

a 3-D array containing the probabilities.

LOSE

a 3-D array containing the standard error calculated for the log odds of the transition probabilities.

lags

a vector containing one-dimensional lags.

type

a character string which specifies that computed probabilities are empirical.

Arguments

data

a categorical data vector of length \(n\).

coords

an \(n \times d\) matrix where each row denotes the \(d\)-D coordinates of data locations.

direction

a \(d\)-D numerical vector (or versor) which represents the chosen direction.

max.dist

a numerical value which defines the maximum lag value. It's Inf by default.

mpoints

a numerical value which defines the number of lag intervals.

tolerance

a numerical value for the tolerance angle (in radians). It's pi/8 by default.

reverse

a logical value. If TRUE the transition probabilities of the reversible chain are also computed. It's FALSE by default.

Author

Luca Sartore drwolf85@gmail.com

Details

Empirical probabilities are estimated by counting such pairs of observations which satisfy some properties, and by normalizing the result.

A generic pair of sample points \(s_i\) and \(s_j\), where \(i \neq j\), must satisfy the following properties:

  • \(\Vert s_i - s_j \Vert \in [a, a+\frac{m}{n}],\) where \(a\) is a non negative real value, while \(m\) denotes the maximum lag value (max.dist) and \(n\) is the number of lag intervals (mpoints).

  • the lag vector \(h = s_i - s_j\) must have the same direction of the vector \(\phi\) (direction) with a certain angular tolerance.

References

Carle, S. F., Fogg, G. E. (1997) Modelling Spatial Variability with One and Multidimensional Continuous-Lag Markov Chains. Mathematical Geology, 29(7), 891-918.

Sartore, L. (2010) Geostatistical models for 3-D data. M.Phil. thesis, Ca' Foscari University of Venice.

See Also

predict.tpfit, predict.tpfit, plot.transiogram

Examples

Run this code
# \donttest{
data(ACM)

# Estimate empirical transition 
# probabilities by points
transiogram(ACM$MAT3, ACM[, 1:3], c(0, 0, 1), 200, 5)
# }

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