# Set up parameters for a single species in a power-law background

Source:`R/newSingleSpeciesParams.R`

`newSingleSpeciesParams.Rd`

This functions creates a `MizerParams`

object with a single
species. This species is embedded in a fixed power-law community spectrum
$$N_c(w) = \kappa w^{-\lambda}$$
This community provides the food income for the species. Cannibalism is
switched off. The predation mortality arises only from the predators in the
power-law community and it is assumed that the predators in the community
have the same feeding parameters as the foreground species. The function has
many arguments, all of which have default values.

## Usage

```
newSingleSpeciesParams(
species_name = "Target species",
w_max = 100,
w_min = 0.001,
eta = 10^(-0.6),
w_mat = w_max * eta,
no_w = log10(w_max/w_min) * 20 + 1,
n = 3/4,
p = n,
lambda = 2.05,
kappa = 0.005,
alpha = 0.4,
h = 30,
beta = 100,
sigma = 1.3,
f0 = 0.6,
fc = 0.25,
ks = NA,
gamma = NA,
ext_mort_prop = 0,
reproduction_level = 0,
R_factor = deprecated(),
w_inf = deprecated(),
k_vb = deprecated()
)
```

## Arguments

- species_name
A string with a name for the species. Will be used in plot legends.

- w_max
Maximum size of species

- w_min
Egg size of species

- eta
Ratio between maturity size

`w_mat`

and maximum size`w_max`

. Default is 10^(-0.6), approximately 1/4. Ignored if`w_mat`

is supplied explicitly.- w_mat
Maturity size of species. Default value is

`eta * w_max`

.- no_w
The number of size bins in the community spectrum. These bins will be equally spaced on a logarithmic scale. Default value is such that there are 20 bins for each factor of 10 in weight.

- n
Scaling exponent of the maximum intake rate.

- p
Scaling exponent of the standard metabolic rate. By default this is equal to the exponent

`n`

.- lambda
Exponent of the abundance power law.

- kappa
Coefficient in abundance power law.

- alpha
The assimilation efficiency.

- h
Maximum food intake rate.

- beta
Preferred predator prey mass ratio.

- sigma
Width of prey size preference.

- f0
Expected average feeding level. Used to set

`gamma`

, the coefficient in the search rate. Ignored if`gamma`

is given explicitly.- fc
Critical feeding level. Used to determine

`ks`

if it is not given explicitly.- ks
Standard metabolism coefficient. If not provided, default will be calculated from critical feeding level argument

`fc`

.- gamma
Volumetric search rate. If not provided, default is determined by

`get_gamma_default()`

using the value of`f0`

.- ext_mort_prop
The proportion of the total mortality that comes from external mortality, i.e., from sources not explicitly modelled. A number in the interval [0, 1).

- reproduction_level
A number between 0 an 1 that determines the level of density dependence in reproduction, see

`setBevertonHolt()`

.- R_factor
- w_inf
- k_vb

## Details

In addition to setting up the parameters, this function also sets up an initial condition that is close to steady state, under the assumption of no fishing.

## See also

Other functions for setting up models:
`newCommunityParams()`

,
`newMultispeciesParams()`

,
`newTraitParams()`

## Examples

```
params <- newSingleSpeciesParams()
sim <- project(params, t_max = 5, effort = 0)
plotSpectra(sim)
```