Add asymptoticMemoryUsage (+ docs/unit-tests)

For additional details, check this thread:
#6

DESCRIPTION

@@ -16,7 +16,7 @@ License: MIT + file LICENSE
 Encoding: UTF-8
 LazyData: true
 RoxygenNote: 6.1.1
-Imports: boot, microbenchmark, ggplot2, stats
+Imports: boot, microbenchmark, bench, ggplot2, stats
 Suggests: 
     testthat (>= 2.1.0),
     covr

R/asymptoticMemoryUsage.R

@@ -0,0 +1,58 @@
+#' Function to compute benchmarked memory allocation with different data sizes for an R expression
+#'
+#' @title Asymptotic Memory Metrics Quantifying function
+#'
+#' @param e An expression which is in the form of a function operating on the parameter 'data.sizes' given by the user.
+#'
+#' @param data.sizes Set of data sizes, which should preferably be a sequence of powers of ten, with a multitude of mid-values included.
+#'                 # Example: data.sizes = 10^(1, 5, by = 0.1)
+#'
+#' @param max.bytes The maximum number of allocated bytes an iteration would be limited upto for the passed expression. (once the limit has been exceeded, further computations on incrementally larger dataset sizes won't be done)
+#'
+#' @return A data frame comprising of the memory usage (in megabytes) computed by bench and the corresponding dataset sizes.
+#'
+#' @export
+#' @import bench
+
+asymptoticMemoryUsage <- function(e, data.sizes, max.bytes)
+{
+  if(!all(!is.infinite(data.sizes) & !is.na(data.sizes) & !is.nan(data.sizes)))
+  {
+    stop("data.sizes must not contain any NA/NaN/Infinite value.")
+  }
+
+  if(length(data.sizes) == 0)
+  {
+    stop("Cannot run on an empty vector for 'data.sizes'.")
+  }
+
+  lang.obj <- substitute(e)
+
+  fun.obj  <- function(data.sizes)
+  {
+    eval(lang.obj)
+  }
+
+  memory.size.limit = ifelse(missing(max.bytes), 10^6, max.bytes)
+
+  l <- length(data.sizes)
+
+  memory.metrics.list <- list()
+
+  for(i in 1:l)
+  {
+    benchmarked.memory.size <- bench_memory(fun.obj(data.sizes[i]))$mem_alloc
+
+    data.size <- data.sizes[i]
+
+    memory.metrics.list[[i]] <- data.frame(c(benchmarked.memory.size), c(data.size))
+
+    ifelse((benchmarked.memory.size > memory.size.limit), break, next)
+  }
+
+  resultant.df <- do.call(rbind, memory.metrics.list)
+
+  colnames(resultant.df) <- c("Memory usage", "Data sizes")
+
+  return(resultant.df)
+}

tests/testthat/test-testsfortestComplexity.R

@@ -50,3 +50,29 @@ test_that("Return value (ggplot object) test for plotTimings", {
   expect_true("ggplot" %in% attributes(plotTimings(df))$class)
 })
 
+# Tests for asymptoticMemoryUsage
+
+test_that("Empty vector/sequence test for data.sizes", {
+  expect_error(asymptoticMemoryUsage(expression, data.sizes = c()))
+  expect_error(asymptoticMemoryUsage(expression, data.sizes = c(NULL)))
+})
+
+test_that("NA test for data.sizes", {
+  expect_error(asymptoticMemoryUsage(expression, data.sizes = c(NA)))
+})
+
+test_that("NaN test for data.sizes", {
+  expect_error(asymptoticMemoryUsage(expression, data.sizes = sqrt(-1)))
+})
+
+test_that("Inf test for data.sizes", {
+  expect_error(asymptoticMemoryUsage(expression, data.sizes = Inf))
+})
+
+test_that("Return value test for asymptoticMemoryUsage", {
+  df <- asymptoticMemoryUsage(rpois(data.sizes, 10), data.sizes = 10)
+  expect_that(df, is_a("data.frame") )
+  expect_equal(dim(df), c(1, 2))
+  expect_equal(attributes(df)$names, c("Memory usage", "Data sizes"))
+})
+