Vectorized Factorization (Complete)

Function for generating the complete factorization for a vector of numbers.

Usage

divisorsRcpp(v, namedList = FALSE, nThreads = NULL)

Arguments

v

Vector of integers or numeric values. Non-integral values will be coerced to whole numbers.

namedList

Logical flag. If TRUE and the length(v) > 1, a named list is returned. The default is FALSE.

nThreads

Specific number of threads to be used. The default is NULL.

Details

Efficient algorithm that builds on primeFactorize to generate the complete factorization of many numbers.

Value

• Returns an unnamed vector if length(v) == 1 regardless of the value of namedList. If \(v < 2^{31}\), the class of the returned vector will be integer, otherwise the class will be numeric.

• If length(v) > 1, a named/unnamed list of vectors will be returned. If max(bound1, bound2) \(< 2^{31}\), the class of each vector will be integer, otherwise the class will be numeric.

References

• Divisor

• 53-bit significand precision

Author

Joseph Wood

Note

The maximum value for each element in \(v\) is \(2^{53} - 1\).

See also

primeFactorize

Examples

## Get the complete factorization of a single number
divisorsRcpp(10^8)
#>  [1]         1         2         4         5         8        10        16
#>  [8]        20        25        32        40        50        64        80
#> [15]       100       125       128       160       200       250       256
#> [22]       320       400       500       625       640       800      1000
#> [29]      1250      1280      1600      2000      2500      3125      3200
#> [36]      4000      5000      6250      6400      8000     10000     12500
#> [43]     15625     16000     20000     25000     31250     32000     40000
#> [50]     50000     62500     78125     80000    100000    125000    156250
#> [57]    160000    200000    250000    312500    390625    400000    500000
#> [64]    625000    781250    800000   1000000   1250000   1562500   2000000
#> [71]   2500000   3125000   4000000   5000000   6250000  10000000  12500000
#> [78]  20000000  25000000  50000000 100000000

## Or get the complete factorization of many numbers
set.seed(29)
myVec <- sample(-1000000:1000000, 1000)
system.time(myFacs <- divisorsRcpp(myVec))
#>    user  system elapsed 
#>   0.001   0.000   0.001 

## Return named list
myFacsWithNames <- divisorsRcpp(myVec, namedList = TRUE)

## Using nThreads
system.time(divisorsRcpp(myVec, nThreads = 2))
#>    user  system elapsed 
#>   0.001   0.000   0.000