Fix RSI when user provides multiple maTypes

The if-statement was checking the formals() of the list, not the
function. The example also needed to be amended because it threw
warnings, which have rightfully begun to be ERRORs in R CMD check.

Fixes #101.

R/RSI.R

@@ -75,8 +75,7 @@
 #' rsiMA1 <- RSI(price, n=14, maType="WMA", wts=ttrc[,"Volume"])
 #'
 #' # Case of two different 'maType's for both MAs
-#' rsiMA2 <- RSI(price, n=14, maType=list(maUp=list(EMA,ratio=1/5),
-#'              maDown=list(WMA,wts=1:10)))
+#' rsiMA2 <- RSI(price, n=14, maType=list(maUp=list(EMA),maDown=list(WMA)))
 #'
 #'
 "RSI" <- 
@@ -114,7 +113,7 @@ function(price, n=14, maType, ...) {
     # If MA function has 'n' arg, see if it's populated in maType;
     # if it isn't, populate it with RSI's formal 'n'
     for(i in 1:length(maType)) {
-      if( !is.null( formals(maType[[i]])$n ) && is.null( maType[[i]]$n ) ) {
+      if( !is.null( formals(maType[[i]][[1]])$n ) && is.null( maType[[i]]$n ) ) {
         maType[[i]]$n <- n
       }
       mavgUp <- do.call( maType[[1]][[1]], c( list(up), maType[[1]][-1] ) )