9  Arguments

9.1 Arguments

9.2 Mandatory argument

  • Arguments that must be supplied with appropriate values while calling the function.

9.3 Default argument value

  • Arguments with default value will be considered if no value is given while calling the function.

9.4 Argument matching

  • Matched by argument names

  • Matched by argument positions

  • Matched by a mix of argument names and positions

  • Partial matching is possible

  • Order of argument matching

    • Check for the exact match
    • Check for the partial match
    • Check for the positional match


9.5 Conduct a t.test

  • The R function t.test peforms one and two sample t-tests on vectors of data.

  • Conduct a t-test to compare if the mean mpg is different between automatic and manual transmission.

Code
set.seed(1234)
n = 20
y1 = round(rnorm(n, 16, 4), 2)
g1 = rep("1", length = n)
y2 = round(rnorm(n, 20, 4), 2)
g2 = rep("2", length = n)

DF = data.frame(y = c(y1, y2), Group = c(g1, g2), stringsAsFactors = TRUE)

t.test(y ~ Group, data = DF, alternative = "two.sided", mu = 0, paired = FALSE, var.equal = FALSE,
    conf.level = 0.95)

t.test(y ~ Group, alternative = "two.sided", paired = FALSE, data = DF, var.equal = FALSE,
    conf.level = 0.95, mu = 0)

t.test(y ~ Group, alt = "two.sided", mu = 0, pa = FALSE, var = FALSE, conf = 0.95,
    dat = DF)

9.6 The ... argument

  • A way to provide further arguments to or from other functions
Code
`?`(cat)
`?`(rep)
`?`(seq)
`?`(paste)
  • Advantage of ... arguments
    • to extend the functionality of another function
    • when the number of arguments passed to the function cannot be known in advance
    • arguments comming after the ... must be named explicitly and cannot be partially matched or matched positionally


9.7 Example: cat

Using cat to concatenate text

Code
cat(1:5, sep = ",")
cat(1:5, sep = ",", fill = FALSE, labels = NULL)
cat(1:5, sep = ",", fill = 5, labels = NULL)
cat(1:5, sep = ",", fill = 2, labels = letters[1:5])

9.8 Function call

Python does not perform partial matching of function arguments like R does. You need to provide the exact argument name when calling a function.