### -----------------------------------------------------------------------
### Programmieren mit statistischer Software (SoSe 2017)
### -----------------------------------------------------------------------


## ----fun1----------------------------------------------------------------
# name <- function(arg_1, arg_2, ...) {
#   statements
# }

## ----fun2----------------------------------------------------------------
# name(expr_1, expr_2)

## ----fun3----------------------------------------------------------------
# ?which.max

which_maxdev <- function(x) {
  mdn <- median(x)
  devs <- abs(x - mdn)
  which.max(devs)
}

## ----fun4----------------------------------------------------------------
data("Forbes2000", package = "HSAUR2")

# summary(Forbes2000$sales)
which_maxdev(Forbes2000$sales)
# Forbes2000$sales[which_maxdev(Forbes2000$sales)]

# summary(Forbes2000$marketvalue)
which_maxdev(Forbes2000$marketvalue)
# Forbes2000$marketvalue[which_maxdev(Forbes2000$marketvalue)]

## ----fun5----------------------------------------------------------------
which_maxdev <- function(x) {
  mdn <- median(x)
  devs <- abs(x - mdn)
  which.max(devs)
  print("Hallo")
}

which_maxdev(Forbes2000$sales)

## ----fun6----------------------------------------------------------------
which_maxdev <- function(x) {
 mdn <- median(x)
 devs <- abs(x - mdn)
 return(which.max(devs))
 print("Hallo")
}

which_maxdev(Forbes2000$sales)

## ----fun7----------------------------------------------------------------
which_maxdev <- function(x) {
  mdn <- median(x)
  devs <- abs(x - mdn)
  which.max(devs)
}

which_maxdev(Forbes2000$profits)

## ----fun8----------------------------------------------------------------
median(Forbes2000$profits)
args(median)

## ----fun9----------------------------------------------------------------
which_maxdev <- function(x, ...) {
  mdn <- median(x, ...)
  devs <- abs(x - mdn)
  which.max(devs)
}

which_maxdev(Forbes2000$profits, na.rm = TRUE)

## ----fun10---------------------------------------------------------------
which_maxdev <- function(x, na.rm = TRUE) {
  mdn <- median(x, na.rm = na.rm)
  devs <- abs(x - mdn)
  which.max(devs)
}

which_maxdev(Forbes2000$profits)

## ----fun11---------------------------------------------------------------
which_maxdev(Forbes2000$sales)
which_maxdev(Forbes2000$sales, FALSE)
# which_maxdev(FALSE, Forbes2000$sales)   # funktioniert nicht

## ----fun12---------------------------------------------------------------
which_maxdev(x = Forbes2000$sales, na.rm = FALSE)
which_maxdev(na.rm = FALSE, x = Forbes2000$sales)
which_maxdev(na.rm = FALSE, Forbes2000$sales)
# teilweise Benennung funktioniert auch

## ----match1--------------------------------------------------------------
which_maxdev(Forbes2000$sales, na.rm = FALSE)
# Jeder Argument-Name darf nur einmal verwendet werden
# which_maxdev(na.rm=Forbes2000$sales, na.rm = FALSE) 
# funktioniert nicht

## ----match2--------------------------------------------------------------
# hier: n statt na.rm
which_maxdev(Forbes2000$sales, n = FALSE)
# which_maxdev(Forbes2000$sales, n = FALSE, na = FALSE) 
# funktioniert nicht

## ----match3--------------------------------------------------------------
which_maxdev(n = FALSE, Forbes2000$sales)
# Unmatched Arguments -> error
which_maxdev(Forbes2000$sales, foo = 1)

## ----check1--------------------------------------------------------------
which_maxdev(Forbes2000$name)
which_maxdev(as.matrix(Forbes2000[, c("sales", "marketvalue")]))
which_maxdev(Forbes2000$sales, na.rm = "yes")

## ----check2--------------------------------------------------------------
which_maxdev <- function(x, na.rm = TRUE) {
  stopifnot(is.numeric(x))
  stopifnot(is.vector(x))
  stopifnot(is.logical(na.rm))

  mdn <- median(x, na.rm = na.rm)
  devs <- abs(x - mdn)
  which.max(devs)
}

which_maxdev(Forbes2000$name)
which_maxdev(as.matrix(Forbes2000[, c("sales", "marketvalue")]))
which_maxdev(Forbes2000$sales, na.rm = "yes")

## ----check3--------------------------------------------------------------
# mit apply()
apply(as.matrix(Forbes2000[, c("sales", "marketvalue")]), 2,
      which_maxdev)

## ----return1-------------------------------------------------------------
which_maxdev <- function(x, na.rm = TRUE) {
  stopifnot(is.numeric(x) & is.vector(x))
  stopifnot(is.logical(na.rm))
  
  mdn <- median(x, na.rm = na.rm)
  devs <- abs(x - mdn)
  return(which.max(devs))
}

## ----return2-------------------------------------------------------------
which_maxdev(Forbes2000$sales)
res <- which_maxdev(Forbes2000$sales)
res

## ----return3-------------------------------------------------------------
which_maxdev <- function(x, na.rm = TRUE) {
  stopifnot(is.numeric(x) & is.vector(x))
  stopifnot(is.logical(na.rm))
  
  mdn <- median(x, na.rm = na.rm)
  devs <- abs(x - mdn)
  invisible(which.max(devs))
}

## ----return4-------------------------------------------------------------
which_maxdev(Forbes2000$sales)
res <- which_maxdev(Forbes2000$sales)
res

## ----scope1--------------------------------------------------------------
f <- function(x) {
  y <- 2 * x
  cat("x =", x, "\n")
  cat("y =", y, "\n")
  cat("z =", z, "\n")
}

## ----scope2--------------------------------------------------------------
# Fehlermeldung, da z nicht definiert ist
f(2)

## ----scope3--------------------------------------------------------------
# Definiton von z
z <- 42
f(2)
# Warnung: Die Verwendung freier Variablen in einer Funktion 
# ist sehr fehleranfaellig 
# und sollte deshalb vermieden werden.