Data commit

Task/Averages-Simple-moving-average/R/averages-simple-moving-average.r

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+#concat concatenates the new values to the existing vector of values, then discards any values that are too old.
+lastvalues <- local(
+{
+   values <- c();
+   function(x, len)
+   {
+      values <<- c(values, x);
+      lenv <- length(values);
+      if(lenv > len) values <<- values[(len-lenv):-1]
+      values
+   }
+})
+
+#moving.average accepts a numeric scalars input (and optionally a length, i.e. the number of values to retain) and calculates the stateful moving average.
+moving.average <- function(latestvalue, len=3)
+{
+   #Check that all inputs are numeric scalars
+   is.numeric.scalar <- function(x) is.numeric(x) && length(x)==1L
+   if(!is.numeric.scalar(latestvalue) || !is.numeric.scalar(len))
+   {
+      stop("all arguments must be numeric scalars")
+   }
+
+   #Calculate mean of variables so far
+   mean(lastvalues(latestvalue, len))
+}
+moving.average(5)  # 5
+moving.average(1)  # 3
+moving.average(-3) # 1
+moving.average(8)  # 2
+moving.average(7)  # 4