BasicRcourseEMC/3-2_Functions1_practical.qmd at main · dnieuw/BasicRcourseEMC · GitHub

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# Functions1: Questions {.unnumbered}

## Function Arguments

::: panel-tabset
### Question 1

Look at the help file for the function `mean()`.

How many arguments does the function have?

What types of vectors are accepted?

What is the default setting for dealing with NA values?
:::

::: panel-tabset
### Question 2

Use the function `mean()` to calculate the mean of the following values:

::: callout-note
note the `NA` and use named argument matching
:::

```{r, eval = F}
c(1, 2, NA, 6)
```
:::

::: panel-tabset
### Question 3

Do Q2 again but rearrange the arguments.
:::

::: panel-tabset
### Question 4

Do Q2 again using positional matching.
:::

::: panel-tabset
### Question 5

Determine the class of `mean()` using `class()`.
:::

::: panel-tabset
### Question 6

Determine the class of `mean()` using `str()`.
:::

::: panel-tabset
### Question 7

Determine the class of the value output in Q4 using `class()`.
:::

::: panel-tabset
### Question 8

Determine the class of the value output in Q4 using str().
:::

## Function environment and scoping

::: panel-tabset
### Question 9

For each of the following sets of commands, give the value that will be returned by the last command. Try to answer without using R.

a)

```{r, eval=F}
w <- 5
f <- function(y) {
  return(w + y)
}
f(y = 2)
```

b)

```{r, eval=F}
w <- 5
f <- function(y) {
  w <- 4
  return(w + y)
}
f(y = 2)
```
:::

::: panel-tabset
### Question 10

Among the variables `w`, `d`, and `y`, which are global to `f()` and which are local? What is the value of z when executing `f(w)`

```{r}
w <- 2
f <- function(y) {
  d <- 3
  h <- function(z) {
    return(z + d)
  }
  return(y * h(y))
}
```
:::

::: panel-tabset
### Question 11

Do the following in R:

a)  Try:

```{r, eval=F}
myFun1 <- function(a) {
  b <- 3
  myFun2(a)
}

myFun2 <- function(y) {
  return(y + a + b)
}

myFun1(10)
```

What happens?

b)  Now try:

```{r, eval=F}
a <- 1
b <- 2
myFun1(10)
```

What happens?
:::