Row-wise iteration like apply with purrr

Question

How do I achieve row-wise iteration using purrr::map?

Here\'s how I\'d do it with a standard row-wise apply.

df <- data.frame(a = 1:10, b = 11:20, c         


        

Answer 1

You are free to always make a wrapper around a function you "like".

rmap <- function (.x, .f, ...) {
    if(is.null(dim(.x))) stop("dim(X) must have a positive length")
    .x <- t(.x) %>% as.data.frame(.,stringsAsFactors=F)
    purrr::map(.x=.x,.f=.f,...)
}

apply the new function rmap (rowwisemap)

rmap(df1,~{
    var1 <- (.x[[1]] + .x[[2]])
    var2 <- .x[[3]]/2
    return(data.frame(var1 = var1, var2 = var2))
    })

Additional Info: (eval from top to bottom)

df1 <- data.frame(a=1:3,b=1:3,c=1:3)
m   <- matrix(1:9,ncol=3)

apply(df1,1,sum)
rmap(df1,sum)

apply(m,1,sum)
rmap(m,sum)

apply(1:10,1,sum)  # intentionally throws an error
rmap(1:10,sum)     # intentionally throws an error