anominate {anominate} R Documentation

## alpha-NOMINATE: Ideal Point Estimator

### Description

Fits the Bayesian (MCMC-based) version of Poole and Rosenthal's NOMINATE model described in Carroll, Lewis, Lo, Poole and Rosenthal, “The Structure of Utility in Spatial Models of Voting,” American Journal of Political Science 57(4): 1008–1028. The method estimates the structure of political actors' utility functions from roll call data with the inclusion of a separate parameter denoted as alpha. alpha values of 1 indicate normal (Gaussian) utility, while alpha values of 0 indicate quadratic utility.

### Usage

```anominate(rcObject, dims=1, nsamp=1000, thin=1, burnin=500, minvotes=20,
lop=0.025, polarity=1, random.starts=TRUE, verbose=FALSE, constrain=FALSE)
```

### Arguments

 `rcObject` An roll call matrix of class `rollcall`, from Simon Jackman's `pscl` package `dims` Number of dimensions to estimate `nsamp` Total number of iterations for the sampler. `nsamp` divided by `thin` must be larger than `burnin`. `thin` Thinning interval `burnin` Number of iterations to be discarded `minvotes` Minimum number of votes required for a legislator to be included in the analysis `lop` A proportion between 0 and 1, the cut-off used for excluding lopsided votes, expressed as the proportion of non-missing votes on the minority side. The default, `lop=0.025`, eliminates votes where the minority is smaller than 2.5 percent `polarity` A vector specifying the row number of the legislator(s) constrained to have a positive (i.e., right-wing or conservative) score on each dimension `random.starts` If `TRUE`, initial values for the legislator and bill parameters are randomly drawn from a uniform distribution. If `FALSE`, the W-NOMINATE estimates are used as the initial values `verbose` If `TRUE`, the progress of the sampler at each 100th iteration is printed to the screen `constrain` If `TRUE`, this constrains alpha=1 and does not estimate it. This option should be used if more than one dimension is being estimated, which makes the method equivalent to a Bayesian implementation of Poole and Rosenthal's (1997) NOMINATE model.

### Value

A list with the following elements:

 `alpha` An object of class `mcmc` with the sampled values of the alpha parameter `beta` An object of class `mcmc` with the sampled values of the beta parameter `legislators` A object of class `mcmc` with the sampled values of the legislator ideal points, with each dimension stored in a separate list (e.g., the first dimension coordinates are stored in `legislators[]`, the second dimension coordinates in `legislators[]`, etc.) `yea.locations` A object of class `mcmc` with the sampled values of the Yea locations (midpoint - spread in W-NOMINATE) for each vote, with each dimension stored in a separate list (e.g., the first dimension coordinates are stored in `yea.locations[]`, the second dimension coordinates in `yea.locations[]`, etc.) `nay.locations` A object of class `mcmc` with the sampled values of the Nay locations (midpoint + spread in W-NOMINATE) for each vote, with each dimension stored in a separate list (e.g., the first dimension coordinates are stored in `nay.locations[]`, the second dimension coordinates in `nay.locations[]`, etc.) `wnom.result` An object of class `nomObject` with the W-NOMINATE results

### Author(s)

Christopher Hare, Royce Carroll, Jeffrey B. Lewis, James Lo, Keith T. Poole and Howard Rosenthal

### References

Carroll, Royce, Jeffrey B. Lewis, James Lo, Keith T. Poole and Howard Rosenthal. 2013. “The Structure of Utility in Spatial Models of Voting.” American Journal of Political Science 57(4): 1008–1028.

Poole, Keith T. and Howard Rosenthal. 1997. Congress: A Political-Economic History of Roll Call Voting. New York: Oxford University Press.

### Examples

```

## Not run:
data(sen111)
sen111_anom <- anominate(sen111, dims=1, polarity=2, nsamp=200, thin=1,
burnin=100, random.starts=FALSE, verbose=TRUE)
summary(sen111_anom)
## Graphical summaries
plot(sen111_anom)
densplot.anominate(sen111_anom)
traceplot.anominate(sen111_anom)

## End(Not run)

```

[Package anominate version 0.6 Index]