r-tmap / r-tmap/tmaptools

get_asp_ratio ignores outside map components

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Description

Is it intentional that get_asp_ratio calculates the ratio based only on the map region, and ignores legends, facet titles, map titles, etc. that are placed outside? Is it possible to include those components in the calculation of aspect ratio?

Consider the following examples:

library(tmap)
data(land, World)
p <- tm_shape(land) + tm_raster("cover") + tm_layout(outer.bg.color = "mistyrose")
asp <- tmaptools::get_asp_ratio(p) # asp = 2

With the calculated aspect ratio of 2:1, there is excessive white space around the map.

tmap_save(p, filename = "test.png", width = 8, height = 8/asp, dpi = 300)

Image

With the legend suppressed, the aspect ratio of 2:1 is perfect.

tmap_save(
  p + tm_layout(legend.show = FALSE), 
  filename = "test-noLegend.png", width = 8, height = 8/asp, dpi = 300
)

Image

We can use asp = 0 to stretch the map frame out to the edges of the image, but this causes excessive margins within the map frame, and leads to a suboptimal legend layout.

tmap_save(p, filename = "test-asp0.png", width = 8, height = 8/asp, dpi = 300, asp=0)

Image

Session Info 
sessioninfo::session_info()
─ Session info ────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
 setting  value
 version  R version 4.4.1 (2024-06-14)
 os       macOS Sonoma 14.7.4
 system   x86_64, darwin20
 ui       X11
 language (EN)
 collate  en_US.UTF-8
 ctype    en_US.UTF-8
 date     2025-03-21
 pandoc   3.6.2 @ /usr/local/bin/pandoc

─ Packages ────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
 package           * version   date (UTC) lib source
 abind               1.4-8     2024-09-12 [1] CRAN (R 4.4.1)
 base64enc           0.1-3     2015-07-28 [1] CRAN (R 4.4.0)
 class               7.3-22    2023-05-03 [2] CRAN (R 4.4.1)
 classInt            0.4-10    2023-09-05 [1] CRAN (R 4.4.1)
 cli                 3.6.3     2024-06-21 [1] CRAN (R 4.4.0)
 codetools           0.2-20    2024-03-31 [2] CRAN (R 4.4.1)
 colorspace          2.1-1     2024-07-26 [1] CRAN (R 4.4.0)
 cols4all            0.8       2024-10-16 [1] CRAN (R 4.4.1)
 crosstalk           1.2.1     2023-11-23 [1] CRAN (R 4.4.0)
 data.table          1.16.2    2024-10-10 [1] CRAN (R 4.4.1)
 DBI                 1.2.3     2024-06-02 [1] CRAN (R 4.4.1)
 dichromat           2.0-0.1   2022-05-02 [1] CRAN (R 4.4.0)
 digest              0.6.37    2024-08-19 [1] CRAN (R 4.4.1)
 e1071               1.7-16    2024-09-16 [1] CRAN (R 4.4.1)
 fastmap             1.2.0     2024-05-15 [1] CRAN (R 4.4.0)
 htmltools           0.5.8.1   2024-04-04 [1] CRAN (R 4.4.0)
 htmlwidgets         1.6.4     2023-12-06 [1] CRAN (R 4.4.0)
 KernSmooth          2.23-24   2024-05-17 [2] CRAN (R 4.4.1)
 lattice             0.22-6    2024-03-20 [2] CRAN (R 4.4.1)
 leafem              0.2.3     2023-09-17 [1] CRAN (R 4.4.0)
 leaflegend          1.2.1     2024-05-09 [1] CRAN (R 4.4.0)
 leaflet             2.2.2     2024-03-26 [1] CRAN (R 4.4.0)
 leaflet.providers   2.0.0     2023-10-17 [1] CRAN (R 4.4.0)
 leafsync            0.1.0     2019-03-05 [1] CRAN (R 4.4.0)
 lwgeom              0.2-14    2024-02-21 [1] CRAN (R 4.4.0)
 magrittr            2.0.3     2022-03-30 [1] CRAN (R 4.4.1)
 microbenchmark      1.5.0     2024-09-04 [1] CRAN (R 4.4.1)
 png                 0.1-8     2022-11-29 [1] CRAN (R 4.4.0)
 proxy               0.4-27    2022-06-09 [1] CRAN (R 4.4.1)
 R6                  2.5.1     2021-08-19 [1] CRAN (R 4.4.0)
 raster              3.6-30    2024-10-02 [1] CRAN (R 4.4.1)
 RColorBrewer        1.1-3     2022-04-03 [1] CRAN (R 4.4.0)
 Rcpp                1.0.13-1  2024-11-02 [1] CRAN (R 4.4.1)
 rlang               1.1.4     2024-06-04 [1] CRAN (R 4.4.0)
 s2                  1.1.7     2024-07-17 [1] CRAN (R 4.4.1)
 sessioninfo         1.2.2     2021-12-06 [1] CRAN (R 4.4.0)
 sf                  1.0-19    2024-11-05 [1] CRAN (R 4.4.1)
 sp                  2.1-4     2024-04-30 [1] CRAN (R 4.4.0)
 spacesXYZ           1.3-0     2024-01-23 [1] CRAN (R 4.4.0)
 stars               0.6-6     2024-07-16 [1] CRAN (R 4.4.0)
 terra               1.8-5     2024-12-12 [1] CRAN (R 4.4.1)
 tmap              * 4.0       2025-01-27 [1] CRAN (R 4.4.1)
 tmaptools           3.2       2025-01-13 [1] CRAN (R 4.4.1)
 units               0.8-5     2023-11-28 [1] CRAN (R 4.4.1)
 viridisLite         0.4.2     2023-05-02 [1] CRAN (R 4.4.0)
 wk                  0.9.3     2024-09-06 [1] CRAN (R 4.4.1)
 XML                 3.99-0.17 2024-06-25 [1] CRAN (R 4.4.0)

 [1] /Users/me/Library/R/x86_64/4.4/library
 [2] /Library/Frameworks/R.framework/Versions/4.4-x86_64/Resources/library

Contributor guide

No contributing guide indexed for this repository

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by inspecting tmaptools::get_asp_ratio and reproducing the documented tmap and tmap_save examples. Trace how the map region, legend, facet titles, and map titles contribute to the current ratio; done means the calculated aspect ratio accounts for the outside components without the excessive whitespace shown.

Written by the indexing model from the issue text.

Assessment

Tech stack
r
Domain
data-visualization
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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