| divide.acs {acs} | R Documentation |
Divide one acs object or variable by another.
Description
The acs package provides a new S4 method for
standard division operations using "/" notation. However, due to the
nature of estimates and errors, there are actually two types of
division, with slightly different meanings: depending on which
variables are being divided, the process may be either a
"proportion"-type division (in which the numerator is a subset of the
denominator) or a "ratio"-type division (in which this is not the
case). When dividing with standard "a/b" notation, the package will
always use the more conservative ratio-type procedure.
When appropriate, "proportion"-type division may be desirable, as it
results in lower standarard errors. To allow users to specify which
type of division to use for acs objects, the package includes a new
"divide.acs" function. (See details.)
Usage
divide.acs(numerator, denominator, method="ratio", verbose=T, output="result")
Arguments
numerator |
an acs object to divide |
denominator |
an acs object to divide by |
method |
either "ratio" (the default) or "proportion", to indicate what kind of division is desired |
verbose |
whether to provide additional warnings or just shut up |
output |
either "result" (the default), "div.method", or "both" |
Details
In certain cases, "proportion-style" division will fail, due to the creation of a negative number under a square root when calculating new standard errors. To address this problem and prevent unnecessary NaN values in the standard.errors, the package implements the recommended Census practice of simply using "ratio-style" division in those cases.
If method="proportion" (not the default) and verbose=T (the default),
division.acs will provide a warning to indicate when
"ratio-style" division has been used, including the number of standard
error cells so affected. Users wishing to examine a detailed,
cell-by-cell report may run divide.acs with the
output="div.method" of output="both" to get additional diagnostic
information.
See "A Compass for Understanding and Using American Community Survey Data" below for details on when this substitution is recommended.
Value
Returns a new acs object with the results of the division (the default), or (when result="div.method") a martix with diagnostic information, or (when result="both"), a list with both of these objects (the first name $result and the second $div.method).
Author(s)
Ezra Haber Glenn eglenn@mit.edu
References
"A Compass for Understanding and Using American Community Survey Data: What State and Local Governments Need to Know." Washington, DC: U.S. Census Bureau. 2009. http://www.census.gov/library/publications/2009/acs/state-and-local.html.