calibrate.rrvglm {VGAM} | R Documentation

## Calibration for CLO models (RR-VGLMs)

### Description

Performs maximum likelihood calibration for constrained linear ordination models (CLO models are better known as RR-VGLMs).

### Usage

    calibrate.rrvglm(object, newdata = NULL,
        type = c("latvar", "predictors", "response", "vcov", "everything"),
        lr.confint = FALSE, cf.confint = FALSE,
        level = 0.95, initial.vals = NULL, ...)

### Arguments

`object` | The fitted `rrvglm` model. Note that `object` should be fitted with corner constraints.
`newdata` | See `calibrate.qrrvglm`.
`type` | See `calibrate.qrrvglm`. If `type = "vcov"` then `object` should have been fitted using `binomialff` or `poissonff` with canonical links, and have `noRRR = ~ 1`.

`lr.confint, cf.confint, level` | Same as `calibrate.qrrvglm`.
`initial.vals` | Same as `calibrate.qrrvglm`. The default is a grid defined by arguments in `calibrate.rrvglm.control`.
`...` | Arguments that are fed into `calibrate.rrvglm.control`.

### Details

Given a fitted regression CLO model, maximum likelihood calibration is theoretically easy and elegant. However, the method assumes that all responses are independent. More details and references are given in Yee (2015).

Calibration requires grouped or non-sparse data as the response. For example, if the family function is `multinomial` then one cannot usually calibrate `y0` if it is a vector of 0s except for one 1. Instead, the response vector should be from grouped data so that there are few 0s. Indeed, it is found empirically that the stereotype model (also known as a reduced-rank `multinomial` logit model) calibrates well only with grouped data, and if the response vector is all 0s except for one 1 then the MLE will probably be at `-Inf` or `+Inf`. As another example, if the family function is `poissonff` then `y0` must not be a vector of all 0s; instead, the response vector should have few 0s ideally. In general, you can use simulation to see what type of data calibrates acceptably.

Internally, this function is a simplification of `calibrate.qrrvglm` and users should look at that function for details. Good initial values are needed, and a grid is constructed to obtain these. The function `calibrate.rrvglm.control` allows the user some control over the choice of these.

### Value

See `calibrate.qrrvglm`. Of course, the quadratic term in the latent variables vanishes for RR-VGLMs, so the model is simpler.

### Warning

See `calibrate.qrrvglm`.

### Note

See `calibrate.qrrvglm` about, e.g., calibration using real-valued responses.

### Author(s)

T. W. Yee

### See Also

`calibrate.qrrvglm`, `calibrate`, `rrvglm`, `weightsvglm`, `optim`, `uniroot`.

### Examples

    ## Not run:   # Example 1
    nona.xs.nz <- na.omit(xs.nz)  # Overkill!! (Data in VGAMdata package)
    nona.xs.nz$dmd     <- with(nona.xs.nz, round(drinkmaxday))
    nona.xs.nz$feethr  <- with(nona.xs.nz, round(feethour))
    nona.xs.nz$sleephr <- with(nona.xs.nz, round(sleep))
    nona.xs.nz$beats   <- with(nona.xs.nz, round(pulse))

    p2 <- rrvglm(cbind(dmd, feethr, sleephr, beats) ~ age + smokenow +
      depressed + embarrassed + fedup + hurt + miserable +  # 11 psychological
      nofriend + moody + nervous + tense + worry + worrier, # variables
      noRRR = ~ age + smokenow, trace = FALSE, poissonff, data = nona.xs.nz,
      Rank = 2)
    cp2 <- calibrate(p2, newdata = head(nona.xs.nz, 9), trace = TRUE)
    cp2

    two.cases <- nona.xs.nz[1:2, ]  # Another calibration example
    two.cases$dmd       <- c(4, 10)
    two.cases$feethr    <- c(4, 7)
    two.cases$sleephr   <- c(7, 8)
    two.cases$beats     <- c(62, 71)
    (cp2b <- calibrate(p2, newdata = two.cases))

    # Example 2
    p1 <- rrvglm(cbind(dmd, feethr, sleephr, beats) ~ age + smokenow +
      depressed + embarrassed + fedup + hurt + miserable +  # 11 psychological
      nofriend + moody + nervous + tense + worry + worrier, # variables
      noRRR = ~ age + smokenow, trace = FALSE, poissonff, data = nona.xs.nz,
      Rank = 1)
    (cp1c <- calibrate(p1, newdata = two.cases, lr.confint = TRUE))

    ## End(Not run)

[Package VGAM version 1.1-1 Index]