Save a flextable as an image

David Gohel

2019/05/23

flextable 0.5.4 is now on CRAN. It contains a new output option that some users were asking: image output. You can now save a flextable as a png or pdf file with function save_as_image.

The solution was existing since a long time but was buried in a stackoverflow question instead of being provided in flextable as an option.

This functionality is letting other options to be available, you can now use method plot and also as_raster and do whatever you’d like with the raster (combine with a ggplot object for example).

Demo

First, let’s create a simple flextable.

library(flextable)
ft <- flextable( head( mtcars ) )
ft <- autofit(ft)
ft

mpg

cyl

disp

hp

drat

wt

qsec

vs

am

gear

carb

21.000

6.000

160.000

110.000

3.900

2.620

16.460

0.000

1.000

4.000

4.000

21.000

6.000

160.000

110.000

3.900

2.875

17.020

0.000

1.000

4.000

4.000

22.800

4.000

108.000

93.000

3.850

2.320

18.610

1.000

1.000

4.000

1.000

21.400

6.000

258.000

110.000

3.080

3.215

19.440

1.000

0.000

3.000

1.000

18.700

8.000

360.000

175.000

3.150

3.440

17.020

0.000

0.000

3.000

2.000

18.100

6.000

225.000

105.000

2.760

3.460

20.220

1.000

0.000

3.000

1.000

You can save it as a png:

save_as_image(ft, path = "name.png")

You can plot it:

plot(ft)

Or combine the table with a ggplot object:

library(ggplot2)
library(grid)
library(cowplot)

ft_raster <- as_raster(ft)

anyplot <- qplot(speed, dist, data = cars, geom = "point")

gflextable <- ggplot() + 
  theme_void() + 
  annotation_custom(rasterGrob(ft_raster), xmin=-Inf, xmax=Inf, ymin=-Inf, ymax=Inf)

plot_grid(anyplot, gflextable, nrow = 2, ncol = 1, rel_heights = c(4, 1) )

About width and height

When a flextable is printed, it may be useful to know the exact width and height of the table to be sure to set up the correct aspect ratio. The function flextable_dim() will provide these informations without the need to produce the image.

dims <- flextable_dim(ft)
dims
#> $widths
#> [1] 7.948045
#> 
#> $heights
#> [1] 2.035298
#> 
#> $aspect_ratio
#> [1] 0.2560753

You can reuse them as values for knitr chunk options fig.asp, fig.width and fig.height.