Presentation ready plots

Lecture 9

Dr. Greg Chism

University of Arizona
INFO 526 - Summer 2024

Setup

# load packages
library(tidyverse)
library(ggrepel)
library(patchwork)
library(ggtext)

# set theme for ggplot2
ggplot2::theme_set(ggplot2::theme_minimal(base_size = 16))

# set figure parameters for knitr
knitr::opts_chunk$set(
  fig.width = 7, # 7" width
  fig.asp = 0.618, # the golden ratio
  fig.retina = 3, # dpi multiplier for displaying HTML output on retina
  fig.align = "center", # center align figures
  dpi = 300 # higher dpi, sharper image
)

Telling a story

Multiple ways of telling a story

  • Sequential plots: Motivation, then resolution

  • A single plot: Resolution, and hidden in it motivation

Project note: you’re asked to create two plots per question. One possible approach: Start with a plot showing the raw data, and show derived quantities (e.g. percent increases, averages, coefficients of fitted models) in the subsequent plot.

Simplicity vs. complexity

When you’re trying to show too much data at once you may end up not showing anything.

  • Never assume your audience can rapidly process complex visual displays

  • Don’t add variables to your plot that are tangential to your story

  • Don’t jump straight to a highly complex figure; first show an easily digestible subset (e.g., show one facet first)

  • Aim for memorable, but clear

Project note: Make sure to leave time to iterate on your plots after you practice your presentation. If certain plots are getting too wordy to explain, take time to simplify them!

Consistency vs. repetitiveness

Be consistent but don’t be repetitive.

  • Use consistent features throughout plots (e.g., same color represents same level on all plots)

  • Aim to use a different type of visualization for each distinct analysis

Designing effective visualizations

Keep it simple

Judging relative area

Use color to draw attention



Tell a story

Leave out non-story details

Order matters

Clearly indicate missing data

Reduce cognitive load

Use descriptive titles

Annotate figures

Plot layout

Sample plots

p_hist <- ggplot(mtcars, aes(x = mpg)) +
  geom_histogram(binwidth = 2)
p_box <- ggplot(mtcars, aes(x = factor(vs), y = mpg)) +
  geom_boxplot()
p_scatter <- ggplot(mtcars, aes(x = disp, y = mpg)) +
  geom_point()
p_text <- mtcars |>
  rownames_to_column() |>
  ggplot(aes(x = disp, y = mpg)) +
  geom_text_repel(aes(label = rowname)) +
  coord_cartesian(clip = "off")

Slide with single plot, little text

The plot will fill the empty space in the slide.

p_hist

Slide with single plot, lots of text

  • If there is more text on the slide

  • The plot will shrink

  • To make room for the text

p_hist

Small fig-width

For a zoomed-in look

```{r}
#| fig-width: 3
#| fig-asp: 0.618

p_hist
```

Large fig-width

For a zoomed-out look

```{r}
#| fig-width: 10
#| fig-asp: 0.618

p_hist
```

fig-width affects text size

Multiple plots on a slide

First, ask yourself, must you include multiple plots on a slide? For example, is your narrative about comparing results from two plots?

  • If no, then don’t! Move the second plot to to the next slide!

  • If yes,

    • Insert columns using the Insert anything tool

    • Use layout-ncol chunk option

    • Use the patchwork package

    • Possibly, use pivoting to reshape your data and then use facets

Columns

Insert > Slide Columns

Quarto will automatically resize your plots to fit side-by-side.

layout-ncol

```{r}
#| fig-width: 5
#| fig-asp: 0.618
#| layout-ncol: 2

p_hist
p_scatter
```

patchwork

```{r}
#| fig-width: 7
#| fig-asp: 0.4

p_hist + p_scatter
```

patchwork layout I

(p_hist + p_box) /
  (p_scatter + p_text)

patchwork layout II

p_text / (p_hist + p_box + p_scatter)

patchwork layout III

p_text + p_hist + p_box + p_scatter + 
  plot_annotation(title = "mtcars", tag_levels = c("A"))

patchwork layout IV

p_text + {
  p_hist + {
    p_box + p_scatter + plot_layout(ncol = 1) + plot_layout(tag_level = 'new')
  }
} + 
  plot_layout(ncol = 1) +
  plot_annotation(tag_levels = c("1","a"), tag_prefix = "Fig ")

More patchwork


Learn more at https://patchwork.data-imaginist.com.

Want to replicate something you saw in my slides?


Look into the source code at https://github.com/INFO-526-SU24/INFO526-SU24/slides/.

🔗 datavizaz-su24