B0_sma function

Intercept of standardized major axis regression (SMA).

It calculates the intercept (B0) for the bivariate linear relationship between predicted and observed values following the SMA regression.

B0_sma(data = NULL, obs, pred, orientation = "PO", tidy = FALSE, na.rm = TRUE)

Arguments

• data: (Optional) argument to call an existing data frame containing the data.
• obs: Vector with observed values (numeric).
• pred: Vector with predicted values (numeric).
• orientation: Argument of class string specifying the axis orientation, PO for predicted vs observed, and OP for observed vs predicted. Default is orientation = "PO".
• tidy: Logical operator (TRUE/FALSE) to decide the type of return. TRUE returns a data.frame, FALSE returns a list; Default : FALSE.
• na.rm: Logic argument to remove rows with missing values (NA). Default is na_rm = TRUE.

Returns

an object of class numeric within a list (if tidy = FALSE) or within a data frame (if tidy = TRUE).

Details

SMA is a symmetric linear regression (invariant results/interpretation to axis orientation) recommended to describe the bivariate scatter instead of OLS regression (classic linear model, which results vary with the axis orientation). For the formula and more details, see online-documentation

Examples

set.seed(1)
X <- rnorm(n = 100, mean = 0, sd = 10)
Y <- rnorm(n = 100, mean = 0, sd = 9)
B0_sma(obs = X, pred = Y)

References

Warton et al. (2006). Bivariate line-fitting methods for allometry. Biol. Rev. Camb. Philos. Soc. 81, 259–291. tools:::Rd_expr_doi("10.1002/1521-4036(200203)44:2<161::AID-BIMJ161>3.0.CO;2-N")