gdalraster (version 1.11.1)

CmbTable-class: Class for counting unique combinations of integers

Description

CmbTable implements a hash table having a vector of integers as the key, and the count of occurrences of each unique integer combination as the value. A unique ID is assigned to each unique combination of input values.

Value

An object of class CmbTable. Contains a hash table having a vector of keyLen integers as the key and the count of occurrences of each unique integer combination as the value, along with methods that operate on the table as described in Details. CmbTable is a C++ class exposed directly to R (via RCPP_EXPOSED_CLASS). Methods of the class are accessed in R using the $ operator.

Arguments

keyLen

The number of integer values comprising each combination.

varNames

Character vector of names for the variables in the combination.

Usage

## Constructors
cmb <- new(CmbTable, keyLen)
# or, with variable names
cmb <- new(CmbTable, keyLen, varNames)

## Methods (see Details) cmb$update(int_cmb, incr) cmb$updateFromMatrix(int_cmbs, incr) cmb$updateFromMatrixByRow(int_cmbs, incr) cmb$asDataFrame() cmb$asMatrix()

Details

new(CmbTable, keyLen) Constructor. Variable names will be assigned as V1, V2, .... Returns an object of class CmbTable.

new(CmbTable, keyLen, varNames) Alternate constructor to specify variable names. Returns an object of class CmbTable.

$update(int_cmb, incr) Updates the hash table for the integer combination in the numeric vector int_cmb (coerced to integer by truncation). If this combination exists in the table, its count will be incremented by incr. If the combination is not found in the table, it will be inserted with count set to incr. Returns the unique ID assigned to this combination. Combination IDs are sequential integers starting at 1.

$updateFromMatrix(int_cmbs, incr) This method is the same as $update() but for a numeric matrix of integer combinations int_cmbs (coerced to integer by truncation). The matrix is arranged with each column vector forming an integer combination. For example, the rows of the matrix could be one row each from a set of keyLen rasters all read at the same extent and pixel resolution (i.e., row-by-row raster overlay). The method calls $update() on each combination (each column of int_cmbs), incrementing count by incr for existing combinations, or inserting new combinations with count set to incr. Returns a numeric vector of length ncol(int_cmbs) containing the IDs assigned to the combinations.

$updateFromMatrixByRow(int_cmbs, incr) This method is the same as $updateFromMatrix() above except the integer combinations are in rows of the matrix int_cmbs (columns are the variables). The method calls $update() on each combination (each row of int_cmbs), incrementing count by incr for existing combinations, or inserting new combinations with count set to incr. Returns a numeric vector of length nrow(int_cmbs) containing the IDs assigned to the combinations.

$asDataFrame() Returns the CmbTable as a data frame with column cmbid containing the unique combination IDs, column count containing the counts of occurrences, and keyLen columns (with names from varNames) containing the integer values comprising each unique combination.

$asMatrix() Returns the CmbTable as a matrix with column 1 (cmbid) containing the unique combination IDs, column 2 (count) containing the counts of occurrences, and columns 3:keyLen+2 (with names from varNames) containing the integer values comprising each unique combination.

Examples

m <- matrix(c(1,2,3,1,2,3,4,5,6,1,3,2,4,5,6,1,1,1), 3, 6, byrow=FALSE)
rownames(m) <- c("layer1", "layer2", "layer3")
print(m)
cmb <- new(CmbTable, 3, rownames(m))
cmb$updateFromMatrix(m, 1)
cmb$asDataFrame()
cmb$update(c(4,5,6), 1)
cmb$update(c(1,3,5), 1)
cmb$asDataFrame()

# same as above but matrix arranged with integer combinations in the rows
m <- matrix(c(1,2,3,1,2,3,4,5,6,1,3,2,4,5,6,1,1,1), 6, 3, byrow=TRUE)
colnames(m) <- c("V1", "V2", "V3")
print(m)
cmb <- new(CmbTable, 3)
cmb$updateFromMatrixByRow(m, 1)
cmb$asDataFrame()
cmb$update(c(4,5,6), 1)
cmb$update(c(1,3,5), 1)
cmb$asDataFrame()