RMarkdown won't knit ggplot2 plot after changing font - r

Question

The plot below was generated in R (without any issue), using this code:
library(tidyverse)
library(extrafont)
loadfonts()
x <- rexp(100)
data.frame(info = x) %>%
ggplot() +
geom_histogram(aes(x = info), col = "red", fill = "red", alpha = 0.5) +
theme_minimal() +
theme(text = element_text(family="LM Roman 10"))
As you can see, the font of the plot is set to "LM Roman 10", which I was able to do thanks to this post and it works perfectly within R.
However when I try to place the image in a LaTeX document using RMarkdown, I get this error:
Quitting from lines 10-22 (min_example.Rmd)
Error in grid.Call.graphics(C_text, as.graphicsAnnot(x$label), x$x, x$y, :
invalid font type
Calls: <Anonymous> ... drawDetails -> drawDetails.text -> grid.Call.graphics
Además: There were 50 or more warnings (use warnings() to see the first 50)
Ejecución interrumpida
Here is the code for min_example.Rmd
---
title: "Untitled"
author: "Javier Rojas"
date: "2/9/2020"
output: pdf_document
---
```{r, echo=FALSE}
library(tidyverse)
library(extrafont)
loadfonts()
x <- rexp(100)
data.frame(info = x) %>%
ggplot() +
geom_histogram(aes(x = info), col = "red", fill = "red", alpha = 0.5) +
theme_minimal() +
theme(text = element_text(family="LM Roman 10"))
```
I am using a Mac computer running macOS High Sierra and R 3.6.1

Answer 1

Usually quite easy to solve. The problem should be, that the font is not installed in your computer.
You have to download the .otf file for the font e.g. (https://fonts2u.com/lmroman10-regular.font) and install it on your Operating System.
If you don't know how to do this, just google it (e.g. "install extra font Windows"), there are plenty of tutorials on it online.
-edit-
I was a little to quick - didn't realize the problem just comes from running it in rmarkdown. Try the following:
```{r, fig.showtext=TRUE, echo=FALSE}
library("tidyverse")
library("showtext")
x <- rexp(100)
font_add("LM Roman 10", regular = "lmroman10-regular.otf")
data.frame(info = x) %>%
ggplot() +
geom_histogram(aes(x = info), col = "red", fill = "red", alpha = 0.5) +
theme_minimal() +
theme(text = element_text(family="LM Roman 10"))
```
It's important that you add fig.showtext=TRUE, library("showtext") and font_add("LM Roman 10", regular = "lmroman10-regular.otf").
I just placed the .otf in my project folder - but I think you can also give it another path.

Answer 2

There exists a current new approach using showtext and showtextdb packages.
On Windows, install manually Latin Modern Roman font (.tff version) following these steps easy instructions https://tex.stackexchange.com/questions/55787/latin-modern-roman-for-ttf. After the installation, you can locate all your fonts in "C:/Windows/Fonts/" just in case.
Once it's already installed, try the following R code to see and example:
install.packages("showtext")
install.packages("showtextdb")
library(showtext)
library(showtextdb)
#set the name and file path
font_add(family = "lmroman10", regular = "C:/Windows/Fonts/lmroman10-regular-webfont.ttf")
showtext_auto()
library(ggplot2)
p = ggplot(NULL, aes(x = 1, y = 1)) + ylim(0.8, 1.2) +
theme(axis.title = element_blank(), axis.ticks = element_blank(),
axis.text = element_blank()) +
annotate("text", 1, 1.1, family = "lmroman10", size = 15,
label = "Text using new font")