basicspace (version 0.17)

blackbox_transpose: Blackbox transpose Scaling

Description

blackbox_transpose is a function that takes a matrix of perceptual data, such as liberal-conservative rankings of various stimuli, and recovers the true location of those stimuli in a spatial model. It differs from procedures such as wnominate, which instead use preference data to estimate candidate and citizen positions. The procedure here generalizes the technique developed by John Aldrich and Richard McKelvey in 1977, which is also included in this package as the aldmck function.

Usage

blackbox_transpose(data,missing=NULL,verbose=FALSE,dims=1,minscale)

Arguments

data

matrix of numeric values, containing the perceptual data. Respondents should be organized on rows, and stimuli on columns. It is helpful, though not necessary, to include row names and column names.

missing

vector or matrix of numeric values, sets the missing values for the data. NA values are always treated as missing regardless of what is set here. Observations with missing data are discarded before analysis. If input is a vector, then the vector is assumed to contain the missing value codes for all the data. If the input is a matrix, it must be of dimension p x q, where p is the maximum number of missing values and q is the number of columns in the data. Each column of the inputted matrix then specifies the missing data values for the respective variables in data. If null (default), no missing values are in the data other than the standard NA value.

verbose

logical, indicates whether aldmck should print out detailed output when scaling the data.

dims

integer, specifies the number of dimensions to be estimated.

minscale

integer, specifies the minimum number of responses a respondent needs needs to provide to be used in the scaling.

Value

An object of class blackbt.

stimuli

vector of data frames of length dims. Each data frame presents results for estimates from that dimension (i.e. x$stimuli[[2]] presents results for dimension 2). Each row contains data on a separate stimulus, and each data frame includes the following variables:

• NNumber of respondents who ranked this stimulus.
• coord1DLocation of the stimulus in the first dimension. If viewing the results for a higher dimension, higher dimension results will appear as coord2D, coord3D, etc.
• R2The percent variance explained for the stimulus. This increases as more dimensions are estimated.

individuals

vector of data frames of length dims. Each data frame presents results for estimates from that dimension (i.e. x$stimuli[[2]] presents results for dimension 2). Individuals that are discarded from analysis due to the minscale constraint are NA'd out. Each row contains data on a separate stimulus, and each data frame includes the following variables:

• cEstimate of the individual intercept.
• w1Estimate of the individual slope. If viewing the results for a higher dimension, higher dimension results will appear as w2, w3, etc.
• R2The percent variance explained for the respondent. This increases as more dimensions are estimated.

fits

A data frame of fit results, with elements listed as follows:

• SSESum of squared errors.
• SSE.explainedExplained sum of squared error.
• percentPercentage of total variance explained.
• SEStandard error of the estimate, with formula provided in the article cited below.
• singularSingluar value for the dimension.

Nrow

Number of rows/stimuli.

Ncol

Number of columns used in estimation. This may differ from the data set due to columns discarded due to the minscale constraint.

Ndata

Total number of data entries.

Nmiss

Number of missing entries.

SS_mean

Sum of squares grand mean.

dims

Number of dimensions estimated.

References

Keith Poole, Jeffrey Lewis, Howard Rosenthal, James Lo, Royce Carroll (2016) ``Recovering a Basic Space from Issue Scales in R.'' Journal of Statistical Software. 69(7), 1--21. doi:10.18637/jss.v069.i07

Keith T. Poole (1998) ``Recovering a Basic Space From a Set of Issue Scales.'' American Journal of Political Science. 42(3), 954-993.

See Also

'plotcdf.blackbt', 'LC1980', 'plot.blackbt', 'summary.blackbt', 'LC1980_bbt'.

Examples

### Loads and scales the Liberal-Conservative scales from the 1980 NES.
data(LC1980)
LCdat=LC1980[,-1]	#Dump the column of self-placements


### This command conducts estimates, which we instead load using data()

#LC1980_bbt <- blackbox_transpose(LCdat,missing=c(0,8,9),dims=3,minscale=5,verbose=TRUE)
data(LC1980_bbt)
plot(LC1980_bbt)

par(ask=TRUE)
plotcdf.blackbt(LC1980_bbt)
summary(LC1980_bbt)