geom_topo() creates a topographical plot as a ggplot2 object. This function automatically combines a number of distinct geom_* and stat_* functions to create a default topographical scalp map. Since geom_raster does not allow unevenly spaced grids, the function creates an interpolated surface.

geom_topo(mapping = NULL, data = NULL, stat = "identity",
  position = "identity", show.legend = NA, na.rm = TRUE,
  inherit.aes = TRUE, interpolate = FALSE, interp_limit = "skirt",
  chan_markers = "point", chan_size = rel(2), head_size = rel(1.5),
  grid_res = 200, method = "biharmonic", ...)



Set of aesthetic mappings created by aes() or aes_(). If specified and inherit.aes = TRUE (the default), it is combined with the default mapping at the top level of the plot. You must supply mapping if there is no plot mapping.


The data to be displayed in this layer. There are three options:

If NULL, the default, the data is inherited from the plot data as specified in the call to ggplot().

A data.frame, or other object, will override the plot data. All objects will be fortified to produce a data frame. See fortify() for which variables will be created.

A function will be called with a single argument, the plot data. The return value must be a data.frame, and will be used as the layer data. A function can be created from a formula (e.g. ~ head(.x, 10)).


The statistical transformation to use on the data for this layer, as a string.


Position adjustment, either as a string, or the result of a call to a position adjustment function.


logical. Should this layer be included in the legends? NA, the default, includes if any aesthetics are mapped. FALSE never includes, and TRUE always includes. It can also be a named logical vector to finely select the aesthetics to display.


If FALSE, the default, missing values are removed with a warning. If TRUE, missing values are silently removed.


If FALSE, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g. borders().


If TRUE interpolate linearly, if FALSE (the default) don't interpolate.


Topoplot with a "skirt" or inside the "head".


Defaults to "point". Mark electrode positions with points or text.


Size for channel markers, if any.


Size of the head shape.


Smoothness of the interpolation grid.


"biharmonic" or ""gam".


Other arguments passed on to layer(). These are often aesthetics, used to set an aesthetic to a fixed value, like colour = "red" or size = 3. They may also be parameters to the paired geom/stat.

See also

Other topoplot functions: stat_scalpmap


library(ggplot2) ggplot(demo_epochs, aes(x = x, y = y, fill = amplitude)) + geom_topo()