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A series over several periods, interactively

Source: R/leaflet.R
leaflet_panels.Rd

The interactive counterpart of map_panels(): every period on one map, one shared scale, and a control to step through them.

Usage

leaflet_panels(
  x,
  values,
  by = NULL,
  coords = NULL,
  crs = NULL,
  titles = NULL,
  kind = c("surface", "probability", "diverging"),
  midpoint = NULL,
  direction = 1,
  label = NULL,
  transform = "auto",
  limits = NULL,
  probs = c(0, 0.99),
  popup = NULL,
  tiles = "Esri.WorldGrayCanvas",
  opacity = 0.8,
  legend = TRUE,
  position = "topright"
)

Arguments

x

The geometry – one grid, drawn once per set of values.

values

The panels. One of:

  • a character vector of column names in x;

  • a matrix with one row per cell and one column per period, which is the form an averaging or posterior step emits – column names become panel titles;

  • a named list of vectors, each in feature order or named by by.

by, coords, crs

Passed to as_map_data(). crs is also the CRS the map is drawn in – see display_crs() for what happens when it is not given.

titles

Panel titles. Taken from the names of values when not given.

kind

How the values are scaled: "surface", "probability" or "diverging".

midpoint, direction

For leaflet_diverging(), as in map_diverging().

label

What to call the quantity in the single shared legend.

transform, limits, probs

Passed to surface_scale(), so the colours match the static map's exactly.

popup

Extra columns of x to show when a cell is clicked, as a character vector. The value and the join key are always shown. FALSE turns popups off.

tiles

A leaflet provider name for the basemap, or NULL for no basemap at all. The default is "Esri.WorldGrayCanvas", a quiet grey one, so the data is the brightest thing on the map rather than competing with a road network. It is also key-free: see the note on leaflet_base().

opacity

How opaque the cells are over the basemap.

legend

Whether to draw the legend.

position

Where the layer control sits.

Value

A leaflet widget.

One legend, and it does not move

The scale is computed once over every period pooled, exactly as in map_panels() – both call the same pooled_spec(), so a cell of a given value is the same colour in the static figure and this one.

Because the scale is shared, the legend is drawn once and left alone rather than tied to each layer. Stepping through the periods changes the map and not the legend, which is what makes the comparison readable: a colour that means 0.4 in spring still means 0.4 in autumn, and the legend sitting still is the visible evidence of that.

It is also the interactive form that suits a series best. Small multiples ask a reader to compare across a page; stepping through them in place compares by change-blindness instead, which is far more sensitive to a small shift and needs no alignment at all.

See also

map_panels(), the static original.

Examples

if (FALSE) { # \dontrun{
grid <- example_grid()
seasons <- cbind(spring = grid$density,
                 summer = grid$density * 2.5,
                 autumn = grid$density * 0.4)

leaflet_panels(grid, seasons, label = "animals per km2")
} # }