monthmean function

Monthly Means

Calculate the monthly mean or adjusted monthly mean for count data.

monthmean(data, resp, offsetpop = NULL, adjmonth = FALSE)

Arguments

• data: data set as a data frame.
• resp: response variable in the data set for which the means will be calculated.
• offsetpop: optional population, used as an offset (default=NULL).
• adjmonth: adjust monthly counts and scale to a 30 day month (‘thirty’ ) or the average month length (‘average’ ) (default=FALSE).

Returns

Returns an object of class Monthmean with the following parts: - mean: a vector of length 12 with the monthly means.

Details

For time series recorded at monthly intervals it is often useful to examine (and plot) the average in each month. When using count data we should adjust the mean to account for the unequal number of days in the month (e.g., 31 in January and 28 or 29 in February).

This function assumes that the data set (data) contains variables for the year and month called year and month, respectively.

Examples

# cardiovascular disease data
data(CVD)
mmean = monthmean(data=CVD, resp='cvd', offsetpop=expression(pop/100000), adjmonth='average')
mmean
plot(mmean)

References

Barnett, A.G., Dobson, A.J. (2010) Analysing Seasonal Health Data. Springer.

See Also

plot.Monthmean

Author(s)

Adrian Barnett a.barnett@qut.edu.au