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Centre and covariance of the Cartesian SSM coordinates for an ellipse layer

Source: R/ssm_draws.R
ssm_ellipse_data.Rd

Compute the five columns geom_ssm_ellipse() draws from: the centre (x0, y0) of a profile's Cartesian coordinates and the elements var_x, var_y, cov_xy of their 2 by 2 covariance matrix. This is an S3 generic; the method for ssm_draws() objects takes the centre from the object's point summaries (results$x_est, results$y_est, the posterior medians of x and y) and the covariance from stats::cov() of the x and y columns of the object's draws. The point geom_ssm_point() draws from the same object is a_est at d_est, which need not coincide with those medians. Objects that retain no draws, such as the result of ssm_analyze(), have no method and are refused.

Usage

ssm_ellipse_data(x, ...)

# S3 method for class 'circumplex_ssm_draws'
ssm_ellipse_data(x, ...)

# Default S3 method
ssm_ellipse_data(x, ...)

Arguments

x

An object of class "circumplex_ssm_draws".

...

Passed to methods; unused by the shipped method.

Value

A one-row data frame with columns x0, y0, var_x, var_y, and cov_xy, in the score metric of the coordinates.

See also

geom_ssm_ellipse(), which draws the ellipse, and ssm_draws(), which produces the input.

Examples

set.seed(1)
draws <- cbind(rnorm(500, 0.4, 0.1), rnorm(500, 0.9, 0.1),
               rnorm(500, -0.3, 0.1))
ssm_ellipse_data(ssm_draws(draws, type = "parameters"))
#>          x0         y0      var_x      var_y        cov_xy
#> 1 0.8978743 -0.3053591 0.01117892 0.01019377 -0.0008221293