Facet with free scales but keep aspect ratio fixed

Question

I am using ggplot to draw faceted maps and have been unable to work out how to allow "free" scales in each facet (so that small regions don't look too small) while keeping the x-y aspect ratio fixed.

Here is a simplified example:

require(maps)
require(ggplot2)

map_nz <- subset(fortify(map_data('nz')),
                 region %in% c("South.Island ", "North.Island "))
gg_nz <- qplot(long, lat, data=map_nz, geom="polygon", group=group)

I now have a plot of the North and South Islands of New Zealand. I can facet this and display it with a fixed aspect ratio like this:

gg_nz + coord_fixed() + facet_wrap(~region)

with a result that looks like this:

NZ map - fixed aspect ratio

Notice that there is quite a bit of space wasted in the North Island facet. I would like it to take up more of the available space. I can free up the scales like this:

gg_nz + facet_wrap(~region, scales="free")

with the following result:

NZ map - free scales

The problem is that the x-y aspect ratio is no longer 1:1 in each facet. I am happy to have each facet on a different scale, but within the facet I would like to preserve the aspect ratio.

I tried the following without success:

gg_nz + facet_wrap(~region, scales="free") + coord_fixed()

Presumably the scale parameter in facet_wrap overrides coord_fixed. Any suggestions?

UPDATE: to give a more dramatic illustration, here is the same phenomenon with some US states:

Fixed coords (using coord_fixed or coord_equal):

US map - Fixed aspect Free coords (using scales = free):

US map -Free scales

Neither of these maps is ideal: in the first, Delaware is tiny. In the second, the aspect ratios are quite distorted. New Jersey, which is a narrow state, is stretched too wide, for example.

I think this is what you are looking for: https://github.com/hadley/ggplot2/issues/187 — Ricardo Saporta, Apr 28 '13 at 05:53
Certainly looks related (although dealing with a more general problem). Doesn't look solved though! — seancarmody, May 01 '13 at 12:18

score 18 · Answer 1 · answered May 30 '17 at 20:18

18

theme(aspect.ratio = 1) works.

gg_nz + facet_wrap(~region, scales="free") + theme(aspect.ratio = 1)

answered May 30 '17 at 20:18

JG11235

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interesting. gets a bit complicated picking the right aspect.ratio value when the variables are not numeric, but this does appear to be a possible solution. – Brian D Aug 14 '20 at 22:42
`theme(aspect.ratio = 1)` sets the aspect of the panel, not the data within it. So if you are plotting with an x range of say 1:10 and y range of 1:1000 aspect.ratio = 1 will set the plot to be square and the actual x axis will be at *10 scale of y axis – Sarah Nov 05 '21 at 01:21

Ricardo Saporta · Answer 2 · 2013-04-28T06:00:42.083

10

UPDATE:

I believe what you are looking for is the ability to crop or zoom into a single facet. In other words, to adjust the ylims and xlims independently for each facet. It looks like such a feature has been requested but not yet implemented (https://github.com/hadley/ggplot2/issues/187)

If the space=free option below does not work, an alternative is to scrap facets and use grid layouts and/or viewports to print each plot manually.

Using facet_grid instead of facet_wrap and adding space=free:

gg_state + facet_grid(~region, scales = "free_x", space="free")

enter image description here

Original Answer:

maybe instead of having both axis scale freely, just have only one scale:

map_state <- subset(fortify(map_data('state')),
                 region %in% c("california", "nevada"))
gg_state <- qplot(long, lat, data=map_state, geom="polygon", group=group)
gg_state + facet_wrap(~region, scales="free_x")

enter image description here

edited Apr 28 '13 at 06:00

answered Apr 28 '13 at 01:35

Ricardo Saporta

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Still not what I am after: the aspect ratio on the left hand side in particular is quite stretched: about 1:2 rather than 1:1. – seancarmody Apr 28 '13 at 05:36
3

gotcha! essentially you want to **crop** one facet, not scale it nor stretch it. Just crop. – Ricardo Saporta Apr 28 '13 at 05:50
Sounds about right, although I'd describe it as scaling while preserving the aspect ratio: sort of a zoom and crop. – seancarmody Apr 28 '13 at 13:14
Thanks for the updated answer; for my problem a very workable solution. – swihart Dec 19 '14 at 17:28

score 1 · Answer 3 · edited May 23 '17 at 12:34

1

Does coord_equal help?

 gg_nz + facet_wrap(~region, scales="free") + coord_equal()

Edit

You could use grid.arrange to manually put the plots on a page, fixing the width and height. This seems to do the trick, but I can't make it work with facet() functionality. Thanks to this post from @mnel.

nz_sth <- qplot(long, lat, data=map_nz[map_nz$region == "South.Island ",], geom="polygon", group=group) + coord_fixed()
nz_nth <- qplot(long, lat, data= map_nz[ map_nz$region == "North.Island " , ] , geom="polygon", group=group) + coord_fixed()


grid.arrange( heights=unit(0.75, "npc") , widths=unit(0.5, "npc") , nz_sth,nz_nth, ncol=2)

enter image description here

edited May 23 '17 at 12:34

Community

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answered Apr 27 '13 at 23:55

Simon O'Hanlon

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`coord_equal` seems to be a synonym for `coord_fixed`. I may not have chosen the best example to see the distortion, but if you look at the South Island on your map, there are 2 degrees between gridlines on both axes and the aspect ratio is not 1:1. – seancarmody Apr 28 '13 at 00:13
@seancarmody hi yes, I see now. I will have a go at this later and see if I can help any. – Simon O'Hanlon Apr 28 '13 at 08:39
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Thanks...it's a tricky one. I was hoping for some kind of `aspect` argument for `facet_wrap`... – seancarmody Apr 28 '13 at 12:56
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Error: coord_fixed doesn't support free scales – user2553813 Sep 13 '19 at 01:40

Facet with free scales but keep aspect ratio fixed

3 Answers3

UPDATE:

Original Answer:

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