desc_vars: Describe Variables

In wjunger/ares: Environmental air pollution epidemiology: a library for time series analysis

Description

Compute some common descriptives statistics of variables

Usage

desc_vars(vars, by = NULL, stats = c("n", "na", "mean", "sd", 
	"min", "max", "centiles"), probs = c(0.25, 0.5, 0.75), 
	labels = NULL, print = TRUE, digits = getOption("digits"), ...)

Arguments

vars	a vector of quoted strings with the variables names or a formula, e.g. ~x+y
by	a factor variable for subset analysis.It will be coerced to a factor. Default is NULL
stats	a vector of quoted strings with the statistics to be computed. See Details
probs	a vector of probabilities for the quantiles computation
labels	a vector of quoted strings with alternate labels for the variables. If omitted vars is used
print	a logical indicating whether the statistics should be printed
digits	an integer indicating the number of decimal places to print. Default is given by the system option digits
...	further arguments for mean, basically, support for trimming

Details

By default, this function computes the following statistics: n: number of observations, na: number of missing values, mean: variable means, sd: standard deviation, min: minimum value; max: maximum value, and centiles: quantiles controlled by the vector probs. Any subset of these statistics can be selected. However, if other than these is indicated it will throw an error. The statistics in stats are not case sensitive.

If the argument by is set, the statistics are computed for each subset defined by the supplied vector.

These statistics are frequently found on publications regarding air pollution and health effects.

Value

The function invisibly returns a data frame with a variable per line and a statistic per column.

Author(s)

Washington Junger [e-mail] and Antonio Ponce de Leon [e-mail]

References

Schwartz, J., Spix, C., Touloumi, G. et al. (1996) Methodological issues in studies of air pollution and daily counts of deaths or hospital admissions. J Epidemiol. Community Health 50 (suppl 1), S12–S18.

Whetherill, G. B. Elementary Statistical Methods. 2 ed. Chapman and Hall.

See Also

summary,mean,quantile

Examples

data(admrio)
setup(admrio,"date")
## no stratified analysis
d <- desc_vars(~resp5+pm10+so2+co,stats=c("n","mean","sd","centiles"),digits=3)
## stratified analysis
d <- desc_vars(~resp5+pm10+so2+co,by=quarters,stats=c("n","mean","sd","centiles"),
	digits=3)

wjunger/ares documentation built on Dec. 23, 2021, 5:17 p.m.