R ggplot, remove white margins in ggsave/ggplot

In this answer linking to this blog post there is a solution which also works for different aspect ratios. You can crop the image on your hard drive, independently of OS:

knitr::plot_crop()

If you're using Unix or Mac OS, another option when the various margin options aren't trimming enough is to use the pdfcrop command available within Unix through R's ability to invoke system commands:

# after saving image, run pdfcrop 
system2(command = "pdfcrop", 
        args    = c("name_or_path_of_file_before_crop.pdf", 
                    "name_or_path_of_file_after_crop.pdf") 
        )

For more, see: https://robjhyndman.com/hyndsight/crop-r-figures/

Found the answer from Remove Plot Margins in ggplot2

theme(plot.margin=grid::unit(c(0,0,0,0), "mm"))

does the job

If pdf and pdfcrop aren't your thing, for example you work in png with a png logo - then see my answer here: How to save a ggplot2 graphic with the proper aspect ratio?