Cumulative Product

Cumulative product, optionally along a single axis. A boolean array is multiplied as zeroes and ones, like base::cumprod() does.

Usage

nv_cumprod(x, axis = NULL, nan_rm = FALSE)

Arguments

x

(arrayish)
One input. Can be any data type. An R value materializes at its default data type.

axis

(integer(1) | NULL)
Axis along which to accumulate. Negative values count from the end, i.e. -1 refers to the last axis. If NULL (default), the input is first flattened to a 1-D array, like base::cumprod().

nan_rm

(logical(1))
How to handle NaN values in float inputs. If FALSE (default), NaN propagates forward from its first occurrence. If TRUE, NaN is treated as the identity element of the cumulative op (0 for sum, 1 for prod, -Inf / +Inf for max / min) and contributes nothing to the running value.

Value

(arrayish)
Has the input's shape when axis is given, and is 1-D of length prod(shape(x)) when axis is NULL, which flattens first. Has the input's data type, except for a boolean input, which is accumulated at the default integer data type (see default_dtypes()).

See also

prim_cumprod() for the underlying primitive.

Examples

x <- nv_matrix(1:6, nrow = 2)
nv_cumprod(x)              # flatten, then accumulate
#> AnvlArray
#>    1
#>    2
#>    6
#>   24
#>  120
#>  720
#> [ CPUi32{6} ] 
nv_cumprod(x, axis = 1L)    # accumulate along rows
#> AnvlArray
#>   1  3  5
#>   2 12 30
#> [ CPUi32{2,3} ] 
nv_cumprod(nv_array(c(2, NaN, 3)))                # NaN propagates
#> AnvlArray
#>    2
#>  nan
#>  nan
#> [ CPUf32{3} ] 
nv_cumprod(nv_array(c(2, NaN, 3)), nan_rm = TRUE) # NaN treated as 1
#> AnvlArray
#>  2
#>  2
#>  6
#> [ CPUf32{3} ]