# Test for differences in a cosinor model between levels of the grouping variable.

Source:`R/test_cosinor.R`

`test_cosinor_levels.Rd`

Given a time variable and optional covariates, generate inference a cosinor fit. For the covariate named (or vector of covariates), this function performs a Wald test comparing the group with covariates equal to 1 to the group with covariates equal to 0. This may not be the desired result for continuous covariates.

## Usage

```
test_cosinor_levels(
x,
x_str,
param = "amp",
comparison_A,
comparison_B,
component_index = 1,
ci_level = 0.95
)
```

## Arguments

- x
An

`cglmm`

object.- x_str
A

`character`

. The name of the grouping variable within which differences in the selected cosinor characteristic (amplitude or acrophase) will be tested.- param
A

`character`

. Either`"amp"`

or`"acr"`

for testing differences in amplitude or acrophase, respectively.- comparison_A
An

`integer, or string`

. Refers to the first level within the grouping variable`x_str`

that is to act as the reference group in the comparison. Ensure that it corresponds to the name of the level in the original dataset.- comparison_B
An

`integer, or string`

. Refers to the second level within the grouping variable`x_str`

that is to act as the comparator group in the comparison. Ensure that it corresponds to the name of the level in the original dataset.- component_index
An

`integer`

. If`comparison_type = "levels"`

,`component_index`

indicates which component is being compared between the levels of the grouping variable.- ci_level
The level for calculated confidence intervals. Defaults to

`0.95`

.

## Examples

```
data_2_component <- simulate_cosinor(
n = 10000,
mesor = 5,
amp = c(2, 5),
acro = c(0, pi),
beta.mesor = 4,
beta.amp = c(3, 4),
beta.acro = c(0, pi / 2),
family = "gaussian",
n_components = 2,
period = c(10, 12),
beta.group = TRUE
)
mod_2_component <- cglmm(
Y ~ group + amp_acro(times,
n_components = 2, group = "group",
period = c(10, 12)
),
data = data_2_component
)
test_cosinor_levels(mod_2_component, param = "amp", x_str = "group")
#> Test Details:
#> Parameter being tested:
#> Amplitude
#>
#> Comparison type:
#> levels
#>
#> Grouping variable used for comparison between groups: group
#> Reference group: 0
#> Comparator group: 1
#>
#> cglmm model has2 components. Component 1 is being used for comparison between groups.
#>
#>
#>
#> Global test:
#> Statistic:
#> 124.11
#>
#> P-value:
#> 0
#>
#>
#> Individual tests:
#> Statistic:
#> 11.14
#>
#> P-value:
#> 0
#>
#> Estimate and 95% confidence interval:
#> 1.02 (0.84 to 1.2)
```