Fast (Grouped, Weighted) Product for Matrix-Like Objects
fprod is a generic function that computes the (column-wise) product of all values in x, (optionally) grouped by g and/or weighted by w. The TRA argument can further be used to transform x using its (grouped, weighted) product.
fprod(x, ...) ## Default S3 method: fprod(x, g = NULL, w = NULL, TRA = NULL, na.rm = .op[["na.rm"]], use.g.names = TRUE, ...) ## S3 method for class 'matrix' fprod(x, g = NULL, w = NULL, TRA = NULL, na.rm = .op[["na.rm"]], use.g.names = TRUE, drop = TRUE, ...) ## S3 method for class 'data.frame' fprod(x, g = NULL, w = NULL, TRA = NULL, na.rm = .op[["na.rm"]], use.g.names = TRUE, drop = TRUE, ...) ## S3 method for class 'grouped_df' fprod(x, w = NULL, TRA = NULL, na.rm = .op[["na.rm"]], use.g.names = FALSE, keep.group_vars = TRUE, keep.w = TRUE, stub = .op[["stub"]], ...)
x: a numeric vector, matrix, data frame or grouped data frame (class 'grouped_df').g: a factor, GRP object, atomic vector (internally converted to factor) or a list of vectors / factors (internally converted to a GRP object) used to group x.w: a numeric vector of (non-negative) weights, may contain missing values.TRA: an integer or quoted operator indicating the transformation to perform: 0 - "na" | 1 - "fill" | 2 - "replace" | 3 - "-" | 4 - "-+" | 5 - "/" | 6 - "%" | 7 - "+" | 8 - "*" | 9 - "%%" | 10 - "-%%". See TRA.na.rm: logical. Skip missing values in x. Defaults to TRUE and implemented at very little computational cost. If na.rm = FALSE a NA is returned when encountered.use.g.names: logical. Make group-names and add to the result as names (default method) or row-names (matrix and data frame methods). No row-names are generated for data.table's.drop: matrix and data.frame method: Logical. TRUE drops dimensions and returns an atomic vector if g = NULL and TRA = NULL.keep.group_vars: grouped_df method: Logical. FALSE removes grouping variables after computation.keep.w: grouped_df method: Logical. Retain product of weighting variable after computation (if contained in grouped_df).stub: character. If keep.w = TRUE and stub = TRUE (default), the weights column is prefixed by "prod.". Users can specify a different prefix through this argument, or set it to FALSE to avoid prefixing....: arguments to be passed to or from other methods. If TRA is used, passing set = TRUE will transform data by reference and return the result invisibly.Non-grouped product computations internally utilize long-doubles in C, for additional numeric precision.
The weighted product is computed as prod(x * w), using a single pass in C. If na.rm = TRUE, missing values will be removed from both x and w i.e. utilizing only x[complete.cases(x,w)] and w[complete.cases(x,w)].
For further computational details see fsum, which works equivalently.
The (w weighted) product of x, grouped by g, or (if TRA is used) x transformed by its (grouped, weighted) product.
fsum, Fast Statistical Functions , Collapse Overview
## default vector method mpg <- mtcars$mpg fprod(mpg) # Simple product fprod(mpg, w = mtcars$hp) # Weighted product fprod(mpg, TRA = "/") # Simple transformation: Divide by product fprod(mpg, mtcars$cyl) # Grouped product fprod(mpg, mtcars$cyl, mtcars$hp) # Weighted grouped product fprod(mpg, mtcars[c(2,8:9)]) # More groups.. g <- GRP(mtcars, ~ cyl + vs + am) # Precomputing groups gives more speed ! fprod(mpg, g) fprod(mpg, g, TRA = "/") # Groupwise divide by product ## data.frame method fprod(mtcars) head(fprod(mtcars, TRA = "/")) fprod(mtcars, g) fprod(mtcars, g, use.g.names = FALSE) # No row-names generated ## matrix method m <- qM(mtcars) fprod(m) head(fprod(m, TRA = "/")) fprod(m, g) # etc.. ## method for grouped data frames - created with dplyr::group_by or fgroup_by mtcars |> fgroup_by(cyl,vs,am) |> fprod() mtcars |> fgroup_by(cyl,vs,am) |> fprod(TRA = "/") mtcars |> fgroup_by(cyl,vs,am) |> fselect(mpg) |> fprod()
Useful links