ggplot flowchart

ggflowchart.qmd

---
output: html_document
editor_options: 
  chunk_output_type: console
---

This is based on Nicola Rennie's blog post https://nrennie.rbind.io/blog/2022-06-06-creating-flowcharts-with-ggplot2/

The flowchart is taken from https://imgur.com/gallery/79VHL


```{r}
library(tidyverse)
library(igraph)
library(showtext)
setwd(here::here('flowchart_ggplot/'))
camcorder::gg_record(
  dir = 'img',
  height = 16,
  width = 16,
  units = 'cm'
)
font_add_google('Fira Sans', 'firasans')
font_add_google('Oleo Script', 'oleo_heading')
showtext_auto()
showtext_opts(dpi = 300)
```

Initial data set containing columns `from` and `to`.

```{r}
dat <- tribble(
 ~from, ~to,
 'Are you a horse?', 'No',
 'Are you a horse?', 'Yes',
 'Are you a horse?', 'Maybe',
 'Maybe', 'How many legs\ndo you walk on?',
 'Yes', 'How many legs\ndo you walk on?',
 'No', 'You\'re not a horse',
 'How many legs\ndo you walk on?', 'Two',
 'How many legs\ndo you walk on?', 'Four',
 'Two', 'You\'re not a horse_2',
 'Four', 'Really?',
 'Really?', 'No_2',
 'Really?', 'Yes_2',
 'No_2', 'Can you read\nand write?',
 'Yes_2', 'Can you read\nand write?',
 'Can you read\nand write?', 'Yes_3',
 'Can you read\nand write?', 'No_3',
 'Yes_3', 'You\'re not a horse_3',
 'No_3', 'You\'re reading this,\naren\'t you?',
 'You\'re reading this,\naren\'t you?', 'Yes_4',
 'Yes_4', 'You\'re not a horse_4'
)
```


Create graph and layout

```{r}
graph <-  graph_from_data_frame(dat, directed = TRUE)
coords <- graph %>% 
  layout_as_tree() %>% 
  as_tibble(.name_repair = ~c('x', 'y'))

output <- coords %>% 
  mutate(
    step = vertex_attr(graph, 'name'),
    label = str_remove(step, '\\_.+'),
    x = -2.5 * x,
    y = 5 * y,
    type = case_when(
      str_detect(label, '\\?') ~ "Question",
      str_detect(step, 'You\'re not a horse') ~ 'Outcome',
      T ~ 'Answer'
    ) 
  )
```

Make boxes

```{r}
box_width <- 1.2
box_height <- 1.25
boxes <- output %>%
  mutate(
    xmin = x - box_width,
    xmax = x + box_width,
    # Adjusted Nicola's code here to make a couple of boxes larger
    ymin = case_when(
      str_detect(step, '(legs|reading|write)') ~ y - 1.5 * box_height,
      T ~ y - box_height
    ),
    ymax = case_when(
      str_detect(step, '(legs|reading|write)') ~ y + 1.5 * box_height,
      T ~ y + box_height
    )
  ) 
```


Make edges

```{r}
# This is the hard part in this plot.
# I only copy-and-pasted this from Nicola's post
edges <- dat %>%
  mutate(id = row_number()) %>%
  pivot_longer(cols = c("from", "to"),
               names_to = "s_e",
               values_to = "step") %>%
  left_join(boxes, by = "step") %>%
  select(-c(label, type, y, xmin, xmax)) %>%
  mutate(y = ifelse(s_e == "from", ymin, ymax)) %>%
  select(-c(ymin, ymax)) %>% 
  # Adjusted Nicola's code here to redirect two arrows
  mutate(
    x = case_when(
      s_e == 'to' & id %in% c(5, 14) ~ x - box_width,
      T ~ x
    )
  )
```


Plotting

```{r}
base_colors <- thematic::okabe_ito(2)
ggplot() +
  geom_path(
    data = edges, 
    aes(x, y, group = id),
    arrow = arrow(length = unit(0.25, 'cm'))
  ) +
  geom_rect(
    data = boxes, 
    aes(
      xmin = xmin,
      xmax = xmax, 
      ymin = ymin, 
      ymax = ymax, 
      fill = type
    )
  ) +
  geom_text(
    data = boxes,
    aes(
      x = x, 
      y = y, 
      label = label
    ),
    lineheight = 1,
    family = 'firasans'
  ) +
  theme_void() +
  theme(
    legend.position = 'none',
    plot.background = element_rect(fill = 'white', colour = NA)
  ) +
  scale_fill_manual(values = c(
    'Question' = base_colors[1],
    'Answer' = colorspace::lighten(base_colors[1], 0.5),
    'Outcome' = colorspace::lighten(base_colors[2], 0.1)
  )) +
  annotate(
    'text',
    x = -1.75,
    y = min(boxes$ymin),
    family = 'firasans',
    hjust = 0,
    vjust = 0,
    lineheight = 1.25,
    label = 'imgur 79VHL\n@rappa753\n@nrennie35'
  ) +
  annotate(
    'text',
    x = -2,
    y = min(boxes$ymin),
    family = 'firasans',
    fontface = 'bold',
    hjust = 1,
    vjust = 0,
    lineheight = 1.25,
    label = 'Inspiration:\nGraphic:\nCode template:'
  ) +
  annotate(
    'text',
    x = -0.3,
    y = min(boxes$ymin) + 11,
    size = 10,
    family = 'oleo_heading',
    hjust = 1,
    vjust = 0,
    lineheight = 1.5,
    label = 'Are you a horse?'
  ) +
  annotate(
    'text',
    x = -0.3,
    y = min(boxes$ymin) + 8.5,
    size = 5.5,
    family = 'oleo_heading',
    hjust = 1,
    vjust = 0,
    lineheight = 1.5,
    label = 'Find out via this flow chart.'
  ) +
  coord_cartesian(
    xlim = c(-4.5, 5)
  )
```