CODEWITHSUNDEEP
rknitr
sluque
sluque

Reputation: 517

chunk options for figure size with knitr::include_graphics are being ignored

Given the following rmarkdown file:

```{r}
library(knitr)
```

```{r, out.width="100%"}
path <- "plotx.png"
knitr::include_graphics(path)
```

```{r, out.width="100%", out.height="150%"}
knitr::include_graphics(path)
```

There's no difference in size between the figures, as if the figure size options are not having any effect. Using other similar options, e.g. fig.width, fig.height, doesn't make any difference.

> sessionInfo()
R version 4.0.2 (2020-06-22)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Debian GNU/Linux bullseye/sid

Matrix products: default
BLAS:   /usr/lib/x86_64-linux-gnu/atlas/libblas.so.3.10.3
LAPACK: /usr/lib/x86_64-linux-gnu/atlas/liblapack.so.3.10.3

locale:
 [1] LC_CTYPE=en_CA.UTF-8       LC_NUMERIC=C               LC_TIME=en_CA.UTF-8        LC_COLLATE=en_CA.UTF-8     LC_MONETARY=en_CA.UTF-8    LC_MESSAGES=en_CA.UTF-8   
 [7] LC_PAPER=en_CA.UTF-8       LC_NAME=C                  LC_ADDRESS=C               LC_TELEPHONE=C             LC_MEASUREMENT=en_CA.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] knitr_1.29          slmisc_1.2.1        latticeExtra_0.6-29 lattice_0.20-41    

loaded via a namespace (and not attached):
 [1] png_0.1-7          mime_0.9           grid_4.0.2         magrittr_1.5       evaluate_0.14      highr_0.8          stringi_1.4.6      RColorBrewer_1.1-2 tools_4.0.2       
[10] stringr_1.4.0      markdown_1.1       jpeg_0.1-8.1       xfun_0.16          yaml_2.2.1         compiler_4.0.2

Upvotes: 1

Views: 2340

Answers (1)

Martin C. Arnold
Martin C. Arnold

Reputation: 9678

For HTML output, setting out.width="100%" will scale the image to 100% width of its parent container, not 100% of the image pixels. Therby the aspect ratio is maintained, giving the largest possible result without distortion. Setting out.width="100%" and out.height="150%" thus produces the same result. Use pixels to get exact dimensions (this may result in distortion).

For LaTeX output, the aspect ratio is maintained, no matter if you use pixels or % (the only difference here is that pixels are treated as pixels and % are translated to scaling factors to \textheight and \linewidth). You may prevent this using the chunk option out.extra='keepaspectratio=false'.

Example:

Image from here.

---
title: "Untitled"
output:
  html_document: default
  pdf_document: default
---

LaTeX and HTML: width = 100px, aspect ratio kept

```{r, out.width = "100px"}
tiger <- "tiger.png"
knitr::include_graphics(tiger)
```

LaTeX: aspect ratio kept, HTML: width = 700px, height = 200px aspect ratio not kept

```{r, out.height = "200px", out.width = "700px"}
knitr::include_graphics(tiger)
```

(LaTeX left, HTML right. Images are scaled to fit side-by-side.)

Upvotes: 6

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