modified lab and slides of loops

lab_loops.Rmd

@@ -184,7 +184,7 @@ dfr.info <- function(dfr) {
 dfr.info(dfr1)
 ```
 
-5. **Extra exercise**  A variation of exercise 3: Create a data frame with three columns: one numeric, one logical, and one character vector. Write a loop that loops over the columns and reports the sum of the column values if it is numeric, the total number of `TRUE`s when is logical and the total number of characters if it is a character vector.
+5. **Extra exercise-loops**. A variation of exercise 3: Create a data frame with three columns: one numeric, one logical, and one character vector. Write a loop that loops over the columns and reports the sum of the column values if it is numeric, the total number of `TRUE`s when is logical and the total number of characters if it is a character vector.
 <details>
   <summary><strong>Tips?</strong></summary>
   To count number of characters, you can use `nchar` function. <br/>
@@ -212,6 +212,26 @@ for(i in 1:ncol(dfr2)) {
 sum.vec
 ```
 
+6. **Extra exercise-functions**. Create a function that will convert time in hours to time in minutes. The function should take a single argument, a numeric value of hours, and return a numeric value of minutes. Add an if clause inside of the function that will stop running the function and give an error if the hours provided are negative. 
+<details>
+  <summary><strong>Tip?</strong></summary>
+  You can read the documentation of the `stop()` function by typing `?stop` in the R console.
+</details>
+
+```{r,accordion=TRUE, error=T}
+hours_to_mins <- function(hours) {
+  if (hours < 0) {
+    stop("Hours cannot be negative")
+  }
+  minutes <- hours * 60
+  return(minutes)
+}
+
+hours_to_mins(3.2)
+#Now test it with a negative hour value
+hours_to_mins(-3.26)
+```
+
 
 6.  In all loops that we tried out we have created the variable where the output is saved outside the loop. Why is this?
 </br>

slide_r_elements_4.Rmd

@@ -593,6 +593,7 @@ h <- function(a = 1, b = d) {
 ---
 
 name: everything_is_a_fn
+exclude:true
 
 # In R everything is a function
 
@@ -602,22 +603,18 @@ Because in R everything is a function
 `+`
 ```
 
---
 
 we can re-define things like this:
 
---
 
 ```{r fns.everything_2, echo=T}
 `+` <- function(e1, e2) { e1 - e2 }
 2 + 2
 ```
 
---
 
 and, finally, clean up the mess...
 
---
 
 ```{r fns.everything_3, echo=T}
 rm("+")