build-parameterized-report

Build Parameterized Report

Create reports that accept parameters to generate multiple customized variations from a single template.

When to Use

• Generating the same report for different departments, regions, or time periods
• Creating client-specific reports from a template
• Building dashboards that filter to specific subsets
• Automating recurring reports with different inputs

Inputs

• Required: Report template (Quarto or R Markdown)
• Required: Parameter definitions (names, types, defaults)
• Optional: List of parameter values for batch generation
• Optional: Output directory for generated reports

Procedure

Step 1: Define Parameters in YAML

For Quarto (report.qmd):

---
title: "Sales Report: `r params$region`"
params:
  region: "North America"
  year: 2025
  include_forecast: true
format:
  html:
    toc: true
---

For R Markdown (report.Rmd):

---
title: "Sales Report"
params:
  region: "North America"
  year: 2025
  include_forecast: true
output: html_document
---

Got: The YAML header contains a params: block with named parameters, each having a default value of the correct type.

If fail: If rendering fails with "object 'params' not found", ensure the params: block is correctly indented under the YAML frontmatter. For Quarto, params must be at the top level of the YAML, not nested under format:.

Step 2: Use Parameters in Code

```{r}
#| label: filter-data

data <- full_dataset |>
  filter(region == params$region, year == params$year)

nrow(data)
```

## Overview for `r params$region`

This report covers the `r params$region` region for `r params$year`.

```{r}
#| label: forecast
#| eval: !expr params$include_forecast

# This chunk only runs when include_forecast is TRUE
forecast_model <- forecast::auto.arima(data$sales)
forecast::autoplot(forecast_model)
```

Got: Code chunks reference parameters via params$name and conditional chunks use #| eval: !expr params$flag for Quarto. Inline R expressions like `r params$region` render dynamic text.