ggsave() does not bolden text, and it changes font of all text instead of just plot title

Question

I'm making a chart in ggplot2 and ggsave() does not do what I expect.

require(ggplot2)
require(showtext)

showtext_auto()
hedFont <- "Pragati Narrow"
font_add_google(
  name = hedFont,
  family = hedFont,
  regular.wt = 400,
  bold.wt = 700
)

chart <- ggplot(
  data = cars,
  aes(
    x = speed,
    y = dist
  )
) +
  geom_point() +
  labs(
    title = "Here is a title",
    subtitle = "Subtitle here"
  ) +
  theme(
    plot.title = element_text(
      size = 20,
      family = hedFont,
      face = "bold"
    ),
    axis.title = element_text(
      face = "bold"
    )
  )

ggsave(
  filename = "myplot",
  plot = chart,
  device = "png",
  path = "~/Desktop",
  width = 300,
  height = 200,
  units = "mm",
  dpi = 72
)

What I expected was for the chart's title to have the custom font. Instead, ggsave() makes a chart where all the text has the font. I expected the axis titles to be bold, but they are not.

Here's what I see in RStudio viewer when I run the ggplot() code in it.

Here's what ggsave() produces.

I want ggsave() to make a chart where only the chart's title has the font and the axes' titles are bold.

UPDATE: I tried Tung's suggestion. I downloaded the Google Font onto my computer. Here's my new code.

font_import(
  paths = "/usr/share/fonts/truetype/google-fonts/",
  recursive = T,
  prompt = F,
  pattern = "Pragati"
)
loadfonts(device = "pdf")
loadfonts(device = "postscript")

myFont <- "Pragati Narrow"

chart <- ggplot(
  data = cars,
  aes(
    x = speed,
    y = dist
  )
) +
  geom_point() +
  labs(
    title = "Here is a title",
    subtitle = "Subtitle here"
  ) +
  theme(
    plot.title = element_text(
      size = 20,
      family = myFont,
      face = "bold"
    ),
    axis.title = element_text(
      face = "bold"
    )
  )

ggsave(
  filename = "myplot2.png",
  plot = chart,
  device = "png",
  path = "~/Desktop",
  width = 300,
  height = 200,
  units = "mm",
  dpi = 72
)

Doesn't seem to have changed anything.

I don't see any errors or warnings in the RStudio console either.

Answer 1

This worked on my Linux Mint Rosa machine. You need to download and import the desired font to extrafont database per this answer

library(extrafont)
library(ggplot2)

hedFont <- "BitstreamVeraSansMono"

chart <- ggplot(
  data = cars,
  aes(
    x = speed,
    y = dist
  )
) +
  geom_point() +
  labs(
    title = "Here is a title",
    subtitle = "Subtitle here"
  ) +
  theme(
    plot.title = element_text(
      size = 20,
      family = hedFont,
      face = "bold"
    ),
    axis.title = element_text(
      face = "bold"
    )
  )
chart

ggsave(
  filename = "./output/myplot.png",
  plot = chart,
  type = "cairo",
  height = 4,
  width = 6,
  dpi = 150)