panels: when to use (by default)?

[mtennekes]

Related to #940

Panel labels can now always be turned off or on by the panel.show argument of tm_layout

The question for now: are you happy with these defaults?

library(tmap)
#> 
#> Attaching package: 'tmap'
#> The following object is masked from 'package:datasets':
#> 
#>     rivers
############################
###### Single map
############################
# default: no panels
tm_shape(World) +
    tm_polygons("HPI")

# with
tm_shape(World) +
    tm_polygons("HPI") +
    tm_layout(panel.show = TRUE)

############################
###### Facets defined with multiple variables
############################
# default: with panels
tm_shape(World) +
    tm_polygons(c("HPI", "footprint"))

# without
tm_shape(World) +
    tm_polygons(c("HPI", "footprint")) +
    tm_layout(panel.show = FALSE)

# default: with panels
tm_shape(World) +
    tm_polygons("HPI") +
    tm_facets("continent")

############################
###### Facets defined with multiple variables, single pages
############################
# default: without
tm_shape(World) +
    tm_polygons(c("HPI", "footprint")) +
    tm_facets_pagewise()

# with
tm_shape(World) +
    tm_polygons(c("HPI", "footprint")) +
    tm_facets_pagewise() +
    tm_layout(panel.show = TRUE)

############################
###### Facets defined with 'by' variable
############################
# default: with
tm_shape(World) +
    tm_polygons("HPI") +
    tm_facets("continent")

# without
tm_shape(World) +
    tm_polygons("HPI") +
    tm_facets("continent") +
    tm_layout(panel.show = FALSE)

############################
###### Facet grid
############################
# default: with panels
tm_shape(World) +
    tm_polygons("HPI") +
    tm_facets_grid("continent", "economy")

# without
tm_shape(World) +
    tm_polygons("HPI") +
    tm_facets_grid("continent", "economy") +
    tm_layout(panel.show = FALSE)

^{Created on 2024-09-26 with reprex v2.1.0}

Imho, the only case in which panels could not be shown by default is the case of multiple variables (third image above). What do you think @Nowosad @Rapsodia86 @olivroy ?

I've also committed this script here https://github.com/r-tmap/tmap/blob/master/tests/testing_panels.Rmd

[Nowosad]

@mtennekes would not it be better if the tm_facets_pagewise also return the panel titles. I can think of two reasons for that:

1. All of the facet types would return panel titles by default (so -- consistency)
2. tm_facets_pagewise may be used for animations, and then panel titles are often neccesary

[Rapsodia86]

I agree with @Nowosad that consistency is important. Whenever any type of tm_facets_ is called, panels should to be visible. I would think that is a logical expectation.

But I understand you point in case of pagewise. Maybe then, move it to a separate function and name tm_pagewise() so maps are shown without a title as default?

In general, I do like the option to turn panels on/off regardless of a case! Great! Thank you very much:)

[mtennekes]

Thx for your input @Nowosad and @Rapsodia86
I've changed the default: now panels are always visible.

A function tm_pagewise would be confusing I guess, same for tm_pages. (Because they are still facets, but printed on different pages.)

I also thought about adding a panel.show argument to tm_facets_x, but prefer not to, because this breaks the tmaps 'grammar of graphics' principles (tm_facets is just to define the facets, and has nothing to do with the plotting).

With the tm_layout(panel.show = FALSE) option it is good enough (otherwise feel free to reopen this issue)