R_Examples

Examples of using the toolkit in R

Demos > R code examples

R code examples

This page describes a basic set of demonstration scripts for using the toolkit in R. The .r files can be found at demos/r in the distributions (from the V1.1 release onwards).

Please see UseInR for instructions on how to begin using the java toolkit from inside R.

Note that these examples use the rJava R library -- you will need to alter them if you want to use another R-Java interface (though I believe this is the standard one).

This page contains the following code examples:

• Example 1 - Transfer entropy on binary data
• Example 2 - Transfer entropy on multidimensional binary data
• Example 3 - Transfer entropy on continuous data using kernel estimators
• Example 4 - Transfer entropy on continuous data using Kraskov estimators
• Example 5 - Multivariate transfer entropy on binary data
• Example 6 - Dynamic dispatch with Mutual info calculator

Example 1 - Transfer entropy on binary data

example1TeBinaryData.r - Simple transfer entropy (TE) calculation on binary data using the discrete TE calculator:

# Load the rJava library and start the JVM
library("rJava")
.jinit()

# Change location of jar to match yours:
#  IMPORTANT -- If using the default below, make sure you have set the working directory
#   in R (e.g. with setwd()) to the location of this file (i.e. demos/r) !!
.jaddClassPath("../../infodynamics.jar")

# Generate some random binary data:
sourceArray<-sample(0:1, 100, replace=TRUE)
destArray<-c(0L, sourceArray[1:99]); # Need 0L to keep as integer array
sourceArray2<-sample(0:1, 100, replace=TRUE)

# Create a TE calculator and run it:
teCalc<-.jnew("infodynamics/measures/discrete/TransferEntropyCalculatorDiscrete", 2L, 1L)
.jcall(teCalc,"V","initialise") # V for void return value
.jcall(teCalc,"V","addObservations",sourceArray, destArray)

result1 <- .jcall(teCalc,"D","computeAverageLocalOfObservations")
cat("For copied source, result should be close to 1 bit : ", result1, "\n")

# Now look at the unrelated source:
.jcall(teCalc,"V","initialise") # V for void return value
.jcall(teCalc,"V","addObservations",sourceArray2, destArray)
result2 <- .jcall(teCalc,"D","computeAverageLocalOfObservations")
cat("For random source, result should be close to 0 bits: ", result2, "\n")

Example 2 - Transfer entropy on multidimensional binary data

example2TeMultidimBinaryData.r - Simple transfer entropy (TE) calculation on multidimensional binary data using the discrete TE calculator.

This example is important for R users, because it shows how to handle multidimensional arrays from R to Java (this is not as simple as single dimensional arrays in example 1 - it requires using extra calls to convert the array).

# Load the rJava library and start the JVM
library("rJava")
.jinit()

# Change location of jar to match yours:
#  IMPORTANT -- If using the default below, make sure you have set the working directory
#   in R (e.g. with setwd()) to the location of this file (i.e. demos/r) !!
.jaddClassPath("../../infodynamics.jar")

# Create many columns in a multidimensional array (2 rows by 100 columns),
#  where the next time step (row 2) copies the value of the column on the left
#  from the previous time step (row 1):
twoDTimeSeriesRtime1 <- sample(0:1, 100, replace=TRUE)
twoDTimeSeriesRtime2 <- c(twoDTimeSeriesRtime1[100], twoDTimeSeriesRtime1[1:99])
twoDTimeSeriesR <- rbind(twoDTimeSeriesRtime1, twoDTimeSeriesRtime2)

# Create a TE calculator and run it:
teCalc<-.jnew("infodynamics/measures/discrete/TransferEntropyCalculatorDiscrete", 2L, 1L)
.jcall(teCalc,"V","initialise") # V for void return value
# Add observations of transfer across one cell to the right per time step:
twoDTimeSeriesJava <- .jarray(twoDTimeSeriesR, "[I", dispatch=TRUE)
.jcall(teCalc,"V","addObservations", twoDTimeSeriesJava, 1L)
result2D <- .jcall(teCalc,"D","computeAverageLocalOfObservations")
cat("The result should be close to 1 bit here, since we are executing copy operations of what is effectively a random bit to each cell here: ", result2D, "\n")

Example 3 - Transfer entropy on continuous data using kernel estimators

example3TeContinuousDataKernel.r - Simple transfer entropy (TE) calculation on continuous-valued data using the (box) kernel-estimator TE calculator.

# Load the rJava library and start the JVM
library("rJava")
.jinit()

# Change location of jar to match yours:
#  IMPORTANT -- If using the default below, make sure you have set the working directory
#   in R (e.g. with setwd()) to the location of this file (i.e. demos/r) !!
.jaddClassPath("../../infodynamics.jar")

# Generate some random normalised data.
numObservations<-1000
covariance<-0.4
sourceArray<-rnorm(numObservations)
destArray = c(0, covariance*sourceArray[1:numObservations-1] + (1-covariance)*rnorm(numObservations-1, 0, 1))
sourceArray2<-rnorm(numObservations) # Uncorrelated source

# Create a TE calculator and run it:
teCalc<-.jnew("infodynamics/measures/continuous/kernel/TransferEntropyCalculatorKernel")
.jcall(teCalc,"V","setProperty", "NORMALISE", "true") # Normalise the individual variables
.jcall(teCalc,"V","initialise", 1L, 0.5) # Use history length 1 (Schreiber k=1), kernel width of 0.5 normalised units
.jcall(teCalc,"V","setObservations", sourceArray, destArray)
# For copied source, should give something close to expected value for correlated Gaussians:
result <- .jcall(teCalc,"D","computeAverageLocalOfObservations")
cat("TE result ",  result, "bits; expected to be close to ", log(1/(1-covariance^2))/log(2), " bits for these correlated Gaussians but biased upwards\n")

.jcall(teCalc,"V","initialise") # Initialise leaving the parameters the same
.jcall(teCalc,"V","setObservations", sourceArray2, destArray)
# For random source, it should give something close to 0 bits
result2 <- .jcall(teCalc,"D","computeAverageLocalOfObservations")
cat("TE result ",  result2, "bits; expected to be close to 0 bits for uncorrelated Gaussians but will be biased upwards\n")

# We can get insight into the bias by examining the null distribution:
nullDist <- .jcall(teCalc,"Linfodynamics/utils/EmpiricalMeasurementDistribution;",
		"computeSignificance", 100L)
cat("Null distribution for unrelated source and destination",
    "(i.e. the bias) has mean", .jcall(nullDist, "D", "getMeanOfDistribution"),
    "bits and standard deviation", .jcall(nullDist, "D", "getStdOfDistribution"),
    ", while the above measurement is beaten by a proportion of", nullDist$pValue, "of the null distribution\n")

Example 4 - Transfer entropy on continuous data using Kraskov estimators

example4TeContinuousDataKraskov.r - Simple transfer entropy (TE) calculation on continuous-valued data using the Kraskov-estimator TE calculator.

# Load the rJava library and start the JVM
library("rJava")
.jinit()

# Change location of jar to match yours:
#  IMPORTANT -- If using the default below, make sure you have set the working directory
#   in R (e.g. with setwd()) to the location of this file (i.e. demos/r) !!
.jaddClassPath("../../infodynamics.jar")

# Generate some random normalised data.
numObservations<-1000
covariance<-0.4
sourceArray<-rnorm(numObservations)
destArray = c(0, covariance*sourceArray[1:numObservations-1] + (1-covariance)*rnorm(numObservations-1, 0, 1))
sourceArray2<-rnorm(numObservations) # Uncorrelated source

# Create a TE calculator:
teCalc<-.jnew("infodynamics/measures/continuous/kraskov/TransferEntropyCalculatorKraskov")
.jcall(teCalc,"V","setProperty", "k", "4") # Use Kraskov parameter K=4 for 4 nearest points

# Perform calculation with correlated source:
.jcall(teCalc,"V","initialise", 1L) # Use history length 1 (Schreiber k=1)
.jcall(teCalc,"V","setObservations", sourceArray, destArray)
result <- .jcall(teCalc,"D","computeAverageLocalOfObservations")
# Note that the calculation is a random variable (because the generated
#  data is a set of random variables) - the result will be of the order
#  of what we expect, but not exactly equal to it; in fact, there will
#  be a large variance around it.
cat("TE result ",  result, "nats; expected to be close to ", log(1/(1-covariance^2)), " nats for these correlated Gaussians\n")

# Perform calculation with uncorrelated source:
.jcall(teCalc,"V","initialise") # Initialise leaving the parameters the same
.jcall(teCalc,"V","setObservations", sourceArray2, destArray)
result2 <- .jcall(teCalc,"D","computeAverageLocalOfObservations")
cat("TE result ",  result2, "nats; expected to be close to 0 nats for uncorrelated Gaussians\n")

# We can also compute the local TE values for the time-series samples here:
#  (See more about utility of local TE in the CA demos)
localTE <- .jcall(teCalc,"[D","computeLocalOfPreviousObservations")
cat("Notice that the mean of locals", sum(localTE)/(numObservations-1),
	"nats equals the above result\n")

Example 5 - Multivariate transfer entropy on binary data

example5TeBinaryMultivarTransfer.r - Multivariate transfer entropy (TE) calculation on binary data using the discrete TE calculator.

# Load the rJava library and start the JVM
library("rJava")
.jinit()

# Change location of jar to match yours:
#  IMPORTANT -- If using the default below, make sure you have set the working directory
#   in R (e.g. with setwd()) to the location of this file (i.e. demos/r) !!
.jaddClassPath("../../infodynamics.jar")

# Generate some random binary data.
numObservations <- 100
sourceArray<-matrix(sample(0:1,numObservations*2, replace=TRUE),numObservations,2)
sourceArray2<-matrix(sample(0:1,numObservations*2, replace=TRUE),numObservations,2)
# Destination variable takes a copy of the first bit of the source in bit 1,
#  and an XOR of the two bits of the source in bit 2:
destArray <- cbind( c(0L, sourceArray[1:numObservations-1,1]), # column 1
		    c(0L, 1L*xor(sourceArray[1:numObservations-1,1],
		                 sourceArray[1:numObservations-1,2]))) # column 2

# Convert the 2D arrays to Java format:
sourceArrayJava <- .jarray(sourceArray, "[I", dispatch=TRUE)
sourceArray2Java <- .jarray(sourceArray2, "[I", dispatch=TRUE)
destArrayJava <- .jarray(destArray, "[I", dispatch=TRUE)

# Create a TE calculator and run it:
teCalc<-.jnew("infodynamics/measures/discrete/TransferEntropyCalculatorDiscrete", 4L, 1L)
.jcall(teCalc,"V","initialise") # V for void return value
# We need to construct the joint values for the dest and source before we pass them in,
#  and need to use the matrix conversion routine when calling from Matlab/Octave:
mUtils<-.jnew("infodynamics/utils/MatrixUtils")
.jcall(teCalc,"V","addObservations",
		.jcall(mUtils,"[I","computeCombinedValues", sourceArrayJava, 2L),
		.jcall(mUtils,"[I","computeCombinedValues", destArrayJava, 2L))
result<-.jcall(teCalc,"D","computeAverageLocalOfObservations")
cat("For source which the 2 bits are determined from, result should be close to 2 bits : ", result, "\n")

.jcall(teCalc,"V","initialise")
.jcall(teCalc,"V","addObservations",
		.jcall(mUtils,"[I","computeCombinedValues", sourceArray2Java, 2L),
		.jcall(mUtils,"[I","computeCombinedValues", destArrayJava, 2L))
result2<-.jcall(teCalc,"D","computeAverageLocalOfObservations")
cat("For random source, result should be close to 0 bits in theory: ", result2, "\n");
cat("Result for random source is inflated towards 0.3 due to finite observation length ",
    .jcall(teCalc,"I","getNumObservations"), "\n",
    "One can verify that the answer is consistent with that from a\n",
    "random source by checking: teCalc.computeSignificance(1000); ans.pValue (for R code see example 3)\n");

Example 6 - Dynamic dispatch with Mutual info calculator

example6DynamicCallingMutualInfo.r - This example shows how to write R code to take advantage of the common interfaces defined for various information-theoretic calculators. Here, we use the common form of the infodynamics.measures.continuous.MutualInfoCalculatorMultiVariate interface (which is never named here) to write common code into which we can plug one of three concrete implementations (kernel estimator, Kraskov estimator or linear-Gaussian estimator) by dynamically supplying the class name of the concrete implementation.

# Load the rJava library and start the JVM
library("rJava")
.jinit()

# Change location of jar to match yours:
#  IMPORTANT -- If using the default below, make sure you have set the working directory
#   in R (e.g. with setwd()) to the location of this file (i.e. demos/r) !!
.jaddClassPath("../../infodynamics.jar")

#---------------------
# 1. Properties for the calculation (these are dynamically changeable, you could
#    load them in from another properties file):
# The name of the data file (relative to this directory)
datafile <- "../data/4ColsPairedNoisyDependence-1.txt"
# List of column numbers for variables 1 and 2:
#  (you can select any columns you wish to be contained in each variable)
variable1Columns <- c(1,2) # array indices start from 1 in R
variable2Columns <- c(3,4)
# The name of the concrete implementation of the interface
#  infodynamics.measures.continuous.MutualInfoCalculatorMultiVariate
#  which we wish to use for the calculation.
# Note that one could use any of the following calculators (try them all!):
#  implementingClass <- "infodynamics/measures/continuous/kraskov/MutualInfoCalculatorMultiVariateKraskov1" # MI([1,2], [3,4]) = 0.36353
#  implementingClass <- "infodynamics/measures/continuous/kernel/MutualInfoCalculatorMultiVariateKernel"
#  implementingClass <- "infodynamics/measures/continuous/gaussian/MutualInfoCalculatorMultiVariateGaussian"
implementingClass <- "infodynamics/measures/continuous/kraskov/MutualInfoCalculatorMultiVariateKraskov1"

#---------------------
# 2. Load in the data
data <- read.csv(datafile, header=FALSE, sep="")
# Pull out the columns from the data set which correspond to each of variable 1 and 2:
variable1 <- data[, variable1Columns]
variable2 <- data[, variable2Columns]
# Extra step to extract the raw values from these data.frame objects:
variable1 <- apply(variable1, 2, function(x) as.numeric(x))
variable2 <- apply(variable2, 2, function(x) as.numeric(x))

#---------------------
# 3. Dynamically instantiate an object of the given class:
# (in fact, all java object creation in octave/matlab is dynamic - it has to be,
#  since the languages are interpreted. This makes our life slightly easier at this
#  point than it is in demos/java/example6LateBindingMutualInfo where we have to handle this manually)
miCalc<-.jnew(implementingClass)

#---------------------
# 4. Start using the MI calculator, paying attention to only
#  call common methods defined in the interface type
#  infodynamics.measures.continuous.MutualInfoCalculatorMultiVariate
#  not methods only defined in a given implementation class.
# a. Initialise the calculator to use the required number of
#   dimensions for each variable:
.jcall(miCalc,"V","initialise", length(variable1Columns), length(variable2Columns))
# b. Supply the observations to compute the PDFs from:
.jcall(miCalc,"V","setObservations",
	.jarray(variable1, "[D", dispatch=TRUE),
	.jarray(variable2, "[D", dispatch=TRUE))
# c. Make the MI calculation:
miValue <- .jcall(miCalc,"D","computeAverageLocalOfObservations")

cat("MI calculator", implementingClass, "\n computed the joint MI as ",
	miValue, "\n")