autoharp

# autoharp
### Vik Gopal

---

# Example Worksheet

.left-column[
<img src="user2021-autoharp_files/figure-html/unnamed-chunk-1-1.png" title="2-panel figure shows pdf and cdf of random variable" alt="2-panel figure shows pdf and cdf of random variable" width="110%" />

]

.right-column[
## Question
Write a function that simulates from the pdf
$$ f(x) = 4x^3 I(0 < x < 1) $$

Run the function to generate `$10^4$` random variates.

## Requirements

- A function named `rf( )`, with two arguments.
- A vector named `X` of length `1e4`.
]

---

Students' code failed to run on our machines because of:

- logical errors,
- packages they used,
- objects wrongly named, or
- incorrect path settings.

]

We wanted a flexible framework to assess:

- correctness of output objects,
- run-time efficiency, and
- R coding expertise.

]

---
class: middle

---

# Testing Correctness Output

---

# Testing Correctness Output

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# Testing Correctness Output

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# Testing Correctness Output

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# Run-time Statistics

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# Static Code Analysis

.pull-left[
<img src="user2021-autoharp_files/figure-html/unnamed-chunk-8-1.png" style="display: block; margin: auto;" />
]

```r
rf <- function (n) {
  
  x <- c ()
  
  for (i in 1:n) {
    
    x [i] <- (runif(1)/4)^(1/3)
    
  }
  
  return (x)
  
}
```

* `igraph` does the plotting.
]

---
# Static Code Analysis

.pull-left[
<img src="user2021-autoharp_files/figure-html/unnamed-chunk-10-1.png" style="display: block; margin: auto;" />
]

```r
rf <- function (n) {
  
* x <- c ()
  
* for (i in 1:n) {
    
*   x [i] <- (runif(1)/4)^(1/3)
    
  }
  
  return (x)
  
}
```

* This code has room for improvement.
]

---

# Static Code Analysis

<img src="user2021-autoharp_files/figure-html/unnamed-chunk-12-1.png" style="display: block; margin: auto;" />
]

<table>
 <thead>
  <tr>
   <th style="text-align:right;"> id </th>
   <th style="text-align:left;"> name </th>
   <th style="text-align:left;"> call_status </th>
   <th style="text-align:left;"> formal_arg </th>
   <th style="text-align:right;"> depth </th>
  </tr>
 </thead>
<tbody>
  <tr>
   <td style="text-align:right;"> 1 </td>
   <td style="text-align:left;"> &lt;- </td>
   <td style="text-align:left;"> TRUE </td>
   <td style="text-align:left;"> FALSE </td>
   <td style="text-align:right;"> 1 </td>
  </tr>
  <tr>
   <td style="text-align:right;"> 2 </td>
   <td style="text-align:left;"> rf </td>
   <td style="text-align:left;"> FALSE </td>
   <td style="text-align:left;"> FALSE </td>
   <td style="text-align:right;"> 2 </td>
  </tr>
  <tr>
   <td style="text-align:right;"> 3 </td>
   <td style="text-align:left;"> function </td>
   <td style="text-align:left;"> TRUE </td>
   <td style="text-align:left;"> FALSE </td>
   <td style="text-align:right;"> 2 </td>
  </tr>
  <tr>
   <td style="text-align:right;"> 4 </td>
   <td style="text-align:left;"> n </td>
   <td style="text-align:left;"> FALSE </td>
   <td style="text-align:left;"> TRUE </td>
   <td style="text-align:right;"> 3 </td>
  </tr>
  <tr>
   <td style="text-align:right;"> 5 </td>
   <td style="text-align:left;"> { </td>
   <td style="text-align:left;"> TRUE </td>
   <td style="text-align:left;"> FALSE </td>
   <td style="text-align:right;"> 3 </td>
  </tr>
  <tr>
   <td style="text-align:right;"> 6 </td>
   <td style="text-align:left;"> &lt;- </td>
   <td style="text-align:left;"> TRUE </td>
   <td style="text-align:left;"> FALSE </td>
   <td style="text-align:right;"> 4 </td>
  </tr>
</tbody>
</table>

<br>

* An R expression is stored as an S4 object.
* The `TreeHarp` object contains node type information.
* Tokenising allows for Natural Language techniques to be applied.
]

---

# Additional Functions

1. It's easy for students to make mistakes such as:
  * slightly different names for objects.
  * incorrect path settings.

1. `autoharp` provides a [shiny app](https://blog.nus.edu.sg/stavg/files/2021/06/soln_checker_v2.mp4) for students to run their code before submission.

2. The `autoharp` was developed for a class on visualisation in R, so 
it contains a function to [generate thumbnails](https://blog.nus.edu.sg/stavg/files/2021/06/thumbnails_v2.mp4) of all the plots created.

---

# Desired Functionality

- Detecting areas for improvement in student scripts, e.g. 
  - duplicated chunks of code within a script.
  - highlighting where piping, or an apply call could be used instead.

```r
x <- f1(w)
y <- f2(x)
z <- f3(y)
```

- Diffs/Visualisations between data frames.

---

### Is the `autoharp` the right package for me?

---

# Alternatives

1. The package helps in the way I create worksheet problems, and grade them.
  * Students submit an entire script, which I run on my end.

1. There are alternative packages out there, e.g.:
  * `markmyassignment`
  * `homework`
  * `learnr`, together with `grade_this`.
  
---
  
# Documentation & Contact Information

1. User manuals (and this deck of slides) can be found at 
https://singator.github.io/autoharp-docs/

2. The `autoharp` ships with a couple of examples of solution templates and 
student scripts that you can try out.

```r
list.files(system.file("examples", package="autoharp"))
```

```
## [1] "question_sheets" "soln_templates"  "student_scripts"
```

2. Feel free to get in touch at **vik.gopal at nus.edu.sg** if you need to.

--
<br>

## Thank you for listening, stay safe and healthy!

---

### P.S.: if you are wondering about the name...

It's the title of a song by Belgian band known as [Hooverphonic](https://www.hooverphonic.com/). I used to listen 
to them a lot (Thanks Claudio!).