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Cumulative logit ordinal response family

Source: R/family.R
cumulative_logit.Rd

cumulative_logit() defines a one-response ordinal model for ordered categories. The first implemented path uses a location formula mu ~ ... and ordered cutpoints with a fixed latent logistic scale. The location intercept is dropped internally, as in standard cumulative-link models, because a free location intercept and free cutpoints are not jointly identifiable.

Usage

cumulative_logit()

Value

A drm_family object.

Details

The implemented contract is Pr(y_i <= k) = logit^-1(theta_k - mu_i), with mu_i = X_mu[i, ] beta_mu and theta[1] < theta[2] < ... < theta[K - 1]. fitted() returns the expected ordered-category score, sum_k k * Pr(y_i = k). Ordinal scale or discrimination formulas are not supported.

The response may be an ordered factor or an integer-coded category. Integer codes are used at face value in increasing numeric order; drmTMB cannot infer whether those numbers represent the scientific ordering the analyst intended. Use an ordered factor when labels carry the biological ordering.

Examples

cumulative_logit()
#> $name
#> [1] "cumulative_logit"
#> 
#> $family
#> [1] "cumulative_logit"
#> 
#> $n_response
#> [1] 1
#> 
#> $dpars
#> [1] "mu"
#> 
#> $links
#>         mu 
#> "identity" 
#> 
#> attr(,"class")
#> [1] "drm_family"