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.
Arguments
- keyLen
The number of integer values comprising each combination.
- varNames
Character vector of names for the variables in the combination.
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.
Usage
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.
$asMatrix()
Returns the CmbTable as a matrix with column 1 (cmbid)
containing the unique combination IDs, column 2 (count)
containing the counts of occurrences, and columns 3:keyLen+2
(with names from varNames) containing the integer values comprising each
unique combination.
Examples
m <- matrix(c(1,2,3,1,2,3,4,5,6,1,3,2,4,5,6,1,1,1), 3, 6, byrow=FALSE)
rownames(m) <- c("layer1", "layer2", "layer3")
print(m)
#> [,1] [,2] [,3] [,4] [,5] [,6]
#> layer1 1 1 4 1 4 1
#> layer2 2 2 5 3 5 1
#> layer3 3 3 6 2 6 1
cmb <- new(CmbTable, 3, rownames(m))
cmb$updateFromMatrix(m, 1)
#> [1] 1 1 2 3 2 4
cmb$asDataFrame()
#> cmbid count layer1 layer2 layer3
#> 1 4 1 1 1 1
#> 2 3 1 1 3 2
#> 3 2 2 4 5 6
#> 4 1 2 1 2 3
cmb$update(c(4,5,6), 1)
#> [1] 2
cmb$update(c(1,3,5), 1)
#> [1] 5
cmb$asDataFrame()
#> cmbid count layer1 layer2 layer3
#> 1 5 1 1 3 5
#> 2 4 1 1 1 1
#> 3 3 1 1 3 2
#> 4 2 3 4 5 6
#> 5 1 2 1 2 3
# 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)
#> V1 V2 V3
#> [1,] 1 2 3
#> [2,] 1 2 3
#> [3,] 4 5 6
#> [4,] 1 3 2
#> [5,] 4 5 6
#> [6,] 1 1 1
cmb <- new(CmbTable, 3)
cmb$updateFromMatrixByRow(m, 1)
#> [1] 1 1 2 3 2 4
cmb$asDataFrame()
#> cmbid count V1 V2 V3
#> 1 4 1 1 1 1
#> 2 3 1 1 3 2
#> 3 2 2 4 5 6
#> 4 1 2 1 2 3
cmb$update(c(4,5,6), 1)
#> [1] 2
cmb$update(c(1,3,5), 1)
#> [1] 5
cmb$asDataFrame()
#> cmbid count V1 V2 V3
#> 1 5 1 1 3 5
#> 2 4 1 1 1 1
#> 3 3 1 1 3 2
#> 4 2 3 4 5 6
#> 5 1 2 1 2 3