Marker or unit circle at the origin

geom_origin() renders a symbol, either a set of crosshairs or a circle, at the origin. geom_unit_circle() renders the unit circle, centered at the origin with radius 1.

geom_origin(
  mapping = NULL,
  data = NULL,
  marker = "crosshairs",
  radius = unit(0.04, "snpc"),
  ...,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = FALSE
)

geom_unit_circle(
  mapping = NULL,
  data = NULL,
  segments = 60,
  scale.factor = 1,
  ...,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = FALSE
)

Arguments

mapping

Set of aesthetic mappings created by 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.

data

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)).

marker

The symbol to be drawn at the origin; matched to "crosshairs" or "circle".

radius

A grid::unit() object that sets the radius of the crosshairs or of the circle.

...

Additional arguments passed to ggplot2::layer().

na.rm

Passed to ggplot2::layer().

show.legend

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.

inherit.aes

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().

segments

The number of segments to be used in drawing the circle.

scale.factor

The circle radius; should remain at its default value 1 or passed the same value as ggbiplot(). (This is an imperfect fix that may be changed in a future version.)

Value

A ggproto layer.

Biplot layers

ggbiplot() uses ggplot2::fortify() internally to produce a single data frame with a .matrix column distinguishing the subjects ("rows") and variables ("cols"). The stat layers stat_rows() and stat_cols() simply filter the data frame to one of these two.

The geom layers geom_rows_*() and geom_cols_*() call the corresponding stat in order to render plot elements for the corresponding factor matrix. geom_dims_*() selects a default matrix based on common practice, e.g. points for rows and arrows for columns.

Aesthetics

geom_origin() accepts no aesthetics. geom_unit_circle() understands the following aesthetics (none required):

• alpha

• colour

• linetype

• size

See also

Other geom layers: geom_axis(), geom_interpolation(), geom_isoline(), geom_lineranges(), geom_rule(), geom_text_radiate(), geom_vector()

Examples

# principal components analysis of glass composition measurements
glass[, c(5L, 7L, 8L, 10L, 11L)] %>%
  princomp(cor = TRUE) %>%
  as_tbl_ord() %>%
  cbind_rows(site = glass$Site, form = glass$Form) %>%
  augment_ord() %>%
  print() -> glass_pca
#> # A tbl_ord of class 'princomp': (68 x 5) x (5 x 5)'
#> # 5 coordinates: Comp.1, Comp.2, ..., Comp.5
#> # 
#> # Rows (principal): [ 68 x 5 | 3 ]
#>   Comp.1  Comp.2 Comp.3 ... |   .element site         form 
#>                             |   <chr>    <chr>        <chr>
#> 1   2.01 0.585    0.940     | 1 score    Bet Eli'ezer Chunk
#> 2   2.55 0.513   -1.71  ... | 2 score    Bet Eli'ezer Chunk
#> 3   1.64 0.0977   0.131     | 3 score    Bet Eli'ezer Chunk
#> 4   1.07 0.00734  1.20      | 4 score    Bet Eli'ezer Chunk
#> 5   1.07 0.00573  1.31      | 5 score    Bet Eli'ezer Chunk
#> # ℹ 63 more rows
#> # 
#> # Columns (standard): [ 5 x 5 | 4 ]
#>   Comp.1 Comp.2  Comp.3 ... |   name  center scale .element
#>                             |   <chr>  <dbl> <dbl> <chr>   
#> 1  0.476  0.383  0.388      | 1 SiO2  71.7   3.16  active  
#> 2  0.488 -0.492 -0.0574 ... | 2 Al2O3  2.64  0.956 active  
#> 3  0.383  0.234 -0.873      | 3 FeO    0.442 0.159 active  
#> 4 -0.425  0.580 -0.153      | 4 MgO    1.15  0.913 active  
#> 5 -0.456 -0.469 -0.247      | 5 CaO    8.18  1.36  active  

# note that column standard coordinates are unit vectors
rowSums(get_cols(glass_pca) ^ 2)
#>  SiO2 Al2O3   FeO   MgO   CaO 
#>     1     1     1     1     1 

# plot column standard coordinates with a unit circle underlaid
glass_pca %>%
  ggbiplot(aes(label = name), sec.axes = "cols") +
  theme_biplot() +
  geom_rows_point(aes(color = site, shape = form), elements = "score") +
  geom_unit_circle(alpha = .5, scale.factor = 3) +
  geom_cols_vector()