---
title: "R Notebook"
output: html_notebook
---



```{r}
library(tidyverse)
library(animation)
```

# Get some robots out

```{r}
df.start <- tibble(point = 1:20) %>%
  mutate(startangle = point / max(point) * 2 * pi,
         x = 20 * cos(startangle),
         y = 20 * sin(startangle),
         direction = startangle - pi / 2) %>% # Turn the robots perpendicular / 90 degrees / pi/2 radians to their position on the circle
  select(-startangle)

df.start %>%
  ggplot(aes(x, y, xend = x + 1 * cos(direction), yend = y + 1 * sin(direction))) +
    geom_segment(arrow = arrow(length = unit(0.2, 'cm'))) +
    coord_equal()  

```

# Generate the full sequence


```{r}
df <- df.start
df.steps <- tibble()

for (step in 1:360) {
  df <- df %>%
    mutate(x = x + 0.5 * cos(direction), # <- Change the stepsize here
           y = y + 0.5 * sin(direction), # <- Change the stepsize here
           direction = direction - (1 / 360) * pi * 2) # Turn one degree
  
  df.steps <- rbind(df.steps,
                    df %>%
                      mutate(step = step))
}

```


# Animation


```{r}
animation_stepsize <- 4

saveGIF({
  
  radius = 40 # max(df.steps$x)
  
  for(i in seq(1, 360, by = animation_stepsize)) {
    p <- df.steps %>%
      filter(step == i) %>%
      ggplot(aes(x, y, color = case_when(point == 1 ~ 'red',
                                         TRUE ~  'black'),
                 xend = x + 1 * cos(direction), yend = y + 1 * sin(direction))) +
        geom_segment(arrow = arrow(length = unit(0.2, 'cm'))) +
        #geom_segment(data = df.steps %>% # <- uncomment this to plot the red robot's path
        #               filter(point %in% c(1))) +
        scale_color_identity() +
        coord_equal(xlim = c(-radius, radius), ylim = c(-radius, radius))
    
    print(p)
  }
  
}, outdir = getwd(), interval = 3 / (360 / animation_stepsize))
```


# The paths of the robots, making a beautiful donut shape


```{r}
df.steps %>%
  ggplot(aes(x, y, color = case_when(point == 1 ~ 'red',
                                         TRUE ~  'black'),
                 xend = x + 1 * cos(direction), yend = y + 1 * sin(direction))) +
    geom_segment() +
    scale_color_identity() +
    coord_equal()
```



# The radius of the circle over time

```{r}
df.steps %>%
  mutate(r = sqrt(x*x + y * y)) %>%
  group_by(step) %>%
  summarize(r = max(r)) %>%
  ggplot(aes(step, r)) +
    geom_line()
```