expandtbl: Expand '2x2 table' into 'data.frame'

In mStats: Epidemiological Data Analysis

Description

expandtbl() generates a data.frame based on vectors.

Usage

expandtbl(
  ...,
  exp_name = "exp",
  exp_lvl = c("exposed", "unexposed"),
  case_name = "case",
  case_lvl = c("case", "control"),
  strata_name = "strata"
)

expandfreq(data, freq)

Arguments

...	vectors
exp_name	Name of exp Variable
exp_lvl	Names of two categories in the order of Exposed and non-exposed
case_name	Name of Case variable
case_lvl	names of two categories in the order of
strata_name	Name of stratified variable
data	frequency table in data.frame
freq	name of variable for the weighted frequency

Details

expandtbl

uses the vectors of 2x2 tables and generates a data frame of at least two columns: exp and case.

expandtbl(c(100, 200, 100, 200))

Strata

Multiple tables can be used to construct a dataset by specifying strata_name as follow. Strata can be included using multiple named vectors.

expandtbl(
             strata1 = c(100, 200, 100, 200),
             strata2 = c(100, 200, 100, 200),
             strata3 = c(100, 200, 100, 200),
             exp_name = "exp",
             exp_lvl = c("exposed", "unexposed"),
             case_name = "case",
             case_lvl = c("case", "control"),
             strata_name = "Strata"
)

Labels for variables

If names or levels of variables are not specified, the followings are applied.

1. exp Name: exp

2. exp levels: exposed and unexposed

3. case Name: case

4. case levels: case and control

5. Strata Name: strata

6. Note: Strata levels are not considered as vectors must be named.

expandfreq() uses the weighted frequencies in data.frame format and construct another data.frame based on the frequency weight. The name of the frequency weighted variable can be specified by freq argument.

Value

data.frame

Functions

• expandfreq: expandfreq() expands a frequency-weighted table into a data.frame.

Author(s)

Email: [e-mail]

Website: https://myominnoo.github.io/

Examples

## Asthma Example from Essential Medical Statistics
## page 160
asthma <- expandtbl(c(81, 995, 57, 867),
              exp_name = "sex",
              exp_lvl = c("woman", "man"),
              case_name = "asthma",
              case_lvl = c("yes", "no"))

## Not run: 
## label variable and dataset
asthma <- label(asthma, "Hypothetical Data of Asthma Prevalence")
asthma <- label(asthma, sex = "Man or Woman",
                           asthma = "Asthma or No Asthma")

## Checking codebook
codebook(asthma)


## simple tabulation
tab(asthma)

## cross-tabulation
tab(asthma, sex, by = asthma)

## End(Not run)


## Example for expanding frequency weighted data

## Example from UCLA website
## you can download the dataset here:
## https://stats.idre.ucla.edu/stat/stata/examples/icda/afterlife.dta

x <- data.frame(gender = c(1, 1, 0, 0),
                 aftlife = c(1, 0, 1, 0),
                 freq = c(435, 147, 375, 134))
y <- expandfreq(x, freq)

## check the numbers by tabulation
## tab(y, gender, by = aftlife)

mStats documentation built on Nov. 23, 2020, 9:07 a.m.