two_source_priors_params: Adjust Bayesian priors - Two Source Trophic Position

Description

Adjust priors for two source trophic position model derived from Post 2002.

Usage

two_source_priors_params(
  a = NULL,
  b = NULL,
  c1 = NULL,
  c1_sigma = NULL,
  c2 = NULL,
  c2_sigma = NULL,
  n1 = NULL,
  n1_sigma = NULL,
  n2 = NULL,
  n2_sigma = NULL,
  dn = NULL,
  dn_sigma = NULL,
  tp_lb = NULL,
  tp_ub = NULL,
  sigma_lb = NULL,
  sigma_ub = NULL,
  bp = FALSE
)

Value

stanvars object to be used with brms() call.

Arguments

a: ($\alpha$) exponent of the random variable for beta distribution. Defaults to 1. See beta distribution for more information.
b: ($\beta$) shape parameter for beta distribution. Defaults to 1. See beta distribution for more information.
c1: mean ($\mu$) prior for the mean of the first $\delta^{13}$C baseline. Defaults to -21.
c1_sigma: variance ($\sigma$)for the mean of the first $\delta^{13}$C baseline. Defaults to 1.
c2: mean ($\mu$) prior for or the mean of the second $\delta^{13}$C baseline. Defaults to -26.
c2_sigma: variance ($\sigma$)for the mean of the first $\delta^{13}$C baseline. Defaults to 1.
n1: mean ($\mu$) prior for the mean of the first $\delta^{15}$N baseline. Defaults to 8.
n1_sigma: variance ($\sigma$)for the mean of the first $\delta^{15}$N baseline. Defaults to 1.
n2: mean ($\mu$) prior for or the mean of the second $\delta^{15}$N baseline. Defaults to 9.5.
n2_sigma: variance ($\sigma$) for the mean of the second $\delta^{15}$N baseline. Defaults to 1.
dn: mean ($\mu$) prior value for $\Delta$N. Defaults to 3.4.
dn_sigma: variance ($\sigma$) for $\delta^{15}$N. Defaults to 0.25.
tp_lb: lower bound for priors for trophic position. Defaults to 2.
tp_ub: upper bound for priors for trophic position. Defaults to 10.
sigma_lb: lower bound for priors for $\sigma$. Defaults to 0.
sigma_ub: upper bound for priors for $\sigma$. Defaults to 10.
bp: logical value that controls whether informed priors are supplied to the model for both $\delta^{15}$N and $\delta^{15}$C baselines. Default is FALSE meaning the model will use uninformed priors, however, the supplied data.frame needs values for both $\delta^{15}$N and $\delta^{15}$C baseline (c1, c2, n1, and n2).

Details

We will use the following equations from Post 2002:

$$\delta^{13}C_c = \alpha * (\delta ^{13}C_1 - \delta ^{13}C_2) + \delta ^{13}C_2$$
$$\delta^{15}N = \Delta N \times (tp - \lambda_1) + n_1 \times \alpha + n_2 \times (1 - \alpha)$$
$$\delta^{15}N = \Delta N \times (tp - (\lambda_1 \times \alpha + \lambda_2 \times (1 - \alpha))) + n_1 \times \alpha + n_2 \times (1 - \alpha)$$

The random exponent ($\alpha$; a) and shape parameters ($\beta$; b) for $\alpha$. This prior assumes a beta distribution.
The mean (c1; $\mu$) and variance (c1_sigma; $\sigma$) of the mean for the first $\delta^{13}C$ for a given baseline. This prior assumes a normal distributions.
The mean (c2;$\mu$) and variance (c2_sigma; $\sigma$) of the mean for the second $\delta^{13}C$ for a given baseline. This prior assumes a normal distributions.
The mean (n1; $\mu$) and variance (n1_sigma; $\sigma$) of the mean for the first $\delta^{15}N$ for a given baseline. This prior assumes a normal distributions.
The mean (n2;$\mu$) and variance (n2_sigma; $\sigma$) of the mean for the second $\delta^{15}$N for a given baseline. This prior assumes a normal distributions.
The mean (dn; $\mu$) and variance (dn_sigma; $\sigma$) of $\Delta$N (i.e, trophic enrichment factor). This prior assumes a normal distributions.
The lower (tp_lb) and upper (tp_ub) bounds for priors for trophic position. This prior assumes a uniform distributions.
The lower (sigma_lb) and upper (sigma_ub) bounds for variance ($\sigma$). This prior assumes a uniform distributions.

Examples

Run this code

two_source_priors_params()

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Description

Usage

Value

Arguments

Details

See Also

Examples