insert side by side png images using knitr

Question

How can I insert side by side png files from my computer into rstudio when creating an html document?

The following works well (plots)

```{r, echo=FALSE,fig.width=4, fig.show='hold'}
 plot(cars)
plot(rnorm(100))
```

But for images from a path, only the last image is displayed

 ```{r fig.width=3, fig.show='hold'}
   library(png)
  img <- readPNG("C:/path to my picture/picture.png")
  grid.raster(img)

  img2 <- readPNG("C:/path to my picture/picture2.png")
  grid.raster(img2)
  ```

Solution 1

You can use knitr::include_graphics() as this one accepts a vector of paths as an argument.

Then you should use fig.show='hold',fig.align='center' in order to plot them on the same line and out.width="49%", out.height="20%" to control the output size.

```{r, echo=FALSE,out.width="49%", 
out.height="20%",fig.cap="caption",fig.show='hold',fig.align='center'}
knitr::include_graphics(c("path/to/img1","path/to/img1"))
``` 

Solution 2

You should learn the syntax of Markdown (really, you need about five minutes). The solution does not even involve R at all:

![](path/to/picture.png) ![](path/to/picture2.png)

BTW, you'd better avoid absolute paths. Use relative paths (relative to your Rmd file).

Solution 3

We still lack a good answer to this question if the desired output is a MS Word document (I see that the OP specifically asked for HTML output, but I'm guessing I'm not the only one who came here looking for a solution that works for MS Word docs also).

Here's one method, based on this and this, but the result is not very satisfactory:

library(png)
library(grid)
library(gridExtra)
img1 <-  rasterGrob(as.raster(readPNG("path/to/picture1.png")), interpolate = FALSE)
img2 <-  rasterGrob(as.raster(readPNG("path/to/picture2.png")), interpolate = FALSE)
grid.arrange(img1, img2, ncol = 2)

Solution 4

One can also use cowplot:

library(cowplot)
ggdraw() + 
  draw_image("path/to/picture1.png", width = 0.5) + 
  draw_image("path/to/picture2.png", width = 0.5, x = 0.5)

Should work for all output formats as well.

View more solutions

Comments

[Climbs_lika_Spyder]

markdown syntax does not allow for adjusting the image size

[Climbs_lika_Spyder]

Worked great for pdf output as well!

[Yihui Xie]

You can use knitr::include_graphics() if you need more sophisticated features in knitr.

[DHW]

As of now, there is markdown syntax for image size adjustment: pandoc.org/MANUAL.html#images

[Naveen Gabriel]

But, it wont print the comment in pdf.

[julianstanley]

There it is. Worked perfectly with HTML output, R 3.5.2, knitr 1.21. Thanks for taking the time to answer an old question.

[Lionel Trebuchon]

Awesome! I can confirm that this works with PDF output too, R 3.5.2, knitr 1.21. Now I am just wondering how to allow for a combined out.width bigger than 100%. Haven't found a solution so far.

[ACG]

And if you're using the here package (you should be using the here package) it's knitr::include_graphics(here("path", "to", c("img1","img2")))

[invictus]

this isn't working for me. I have: knitr::include_graphics(c("a.gif","b.gif")). Paths are correct (it works if I do ![](a.gif))

[EA304GT]

Also worth reading the corresponding bookdown documentation

[Saren Tasciyan]

How to put 2 images side by side but both with different height/width?

[Leonardo Donato Nunes]

To adjust the image size you can use ![](path/to/picture.png) {width=110px}

[Adel]

What is rasterGrob doing? What is the difference with img <- readPNG?