Passing a character-element to render() to create several different PDFs - r

Question

I try to create a number of PDFs with Markdown which all look the same, but use different data. For this purpose I created a little bit of code to generate random data which should be used in the creation of the PDF-File.
library(tidyverse)
r_sample <- seq(1, 5, by = 0.1)
nr_rows <- 10
df_names <- vector()
for(i in 1:2){
name <- paste0("i_",i)
i_sample <- tibble("Name" = paste0("i_", seq(1:nr_rows)))
i_sample <- i_sample %>% add_column(sample(r_sample, nr_rows, replace = TRUE)) %>%
rename("Value" = "sample(r_sample, nr_rows, replace = TRUE)")
assign(name, i_sample)
df_names[i] <- name
}
The Markdown-Script is almost empty, since it is just used for testing purposes.
---
title: "Test"
output: pdf_document
params:
data : ""
---
This is just a Test.
```{r echo = FALSE}
params$data
```. #error made intentionally!
Now I try to get the data from my R-Script into the Markdown-Script using render(). Since I want to loop over the different dataframes, I wrote a simple loop.
for(i in 1:2){
rmarkdown::render('Test.Rmd', params = list(data = df_names[i]),
output_file = glue::glue(paste0("file_", df_names[i], ".pdf")))
}
Now to the problem. Markdown understands the input of env_names[i] as a character and not as the dataframe. However if I type it manually like this:
rmarkdown::render('Test.Rmd', params = list(data = i_1), output_file = glue::glue(paste0("file_i_1.pdf")))
it works. I understand the problem, but I can't find a way to work around this.
If anyone could help I would be very glad! Thanks in advance.

Answer 1

The direct fix for the problem at hand is to wrap df_names[i] in get() in order to access the object whose name matches df_names[i] instead of passing the value of df_names[i] to render():
rmarkdown::render('Test.Rmd', params = list(data = get(df_names[i])),
output_file = glue::glue(paste0("file_", df_names[i], ".pdf")))
Yet, dynamically creating objects using assign in the global environment is rather unidiomatic in R – and not doing this also eradicates the need for using get() afterwards.
Therefore, I propose to write the code snippet from the question as follows:
r_sample <- seq(1, 5, by = 0.1)
nr_rows <- 10
df_list <- list()
for(i in 1:2){
df_list[[i]] <- tibble(Name = paste0("i_", seq(1:nr_rows)), Value = sample(r_sample, nr_rows, replace = TRUE))
}
Then, the loop render the documents becomes:
for(i in 1:2){
rmarkdown::render('Test.Rmd', params = list(data = df_list[[i]]),
output_file = paste0("file_i_", i, ".pdf"))
}