Quarto figures with height calculated from data rows

quarto_plot_height.qmd

---
title: "Plot height test"
format: 
  html:
    embed-resources: true
---

With parametrized Quarto reports, certain figures are expected to grow or shrink in widht/height based on existing data. This Quarto report demonstrates how to automatically adjust figure height based on the number of rows present in data. A horizontal column plot (where Y values are groups and X values are a continuous variable, so that bars grow sideways) of fixed height would simply shrink all columns to make them fit in the default height, but in this example, the plot height itself will increase according to the number of rows, so that all plots will have roughly the same column widths.

```{r setup}
library(ggplot2)

rows <- 23
```

Data will have `{r} rows` rows.

```{r data}
data <- data.frame(
  group = letters[1:rows],
  values = sample(10:90, rows, replace = TRUE)
)
```

```{r height}
base <- 0.3
height <- base * nrow(data)
```

Based on `{r} nrow(data)` rows, with a base height of `{r} base` per row, plot height will be `{r} height`.

```{r plot}
#| fig-height: !expr height
#| fig-width: 5
data |> 
  ggplot() +
  aes(values, group) +
  geom_col() +
  theme_classic()
```