wq (version 0.2-9)

wqData: Construct an object of class "WqData"

Description

wqData is a constructor for the "WqData" class that is often more convenient to use than new. It converts a data.frame containing water quality data in long or wide format to a "WqData" object. In long format, observations are all in one column and a second column is used to designate the variable being observed. In wide format, observations for each variable are in a separate column.

Usage

wqData(data, locus, wqdata, site.order, time.format = "%Y-%m-%d", 
        type = c("long", "wide"))

Value

An object of class "WqData".

Rdversion

1.1

Details

If the data are already in long format, the function has little to do but rename the data fields. If in wide format, the reshape package is called to melt the data. The function also removes NA observations, converts site to (possibly ordered) factors with valid variable names, and converts time to class "Date" or "POSIXct" and ISO 8601 format, depending on time.format.

References

International Organization for Standardization (2004) ISO 8601. Data elements and interchange formats - Information interchange - Representation of dates and times. http://www.iso.org/iso/en/prods-services/popstds/datesandtime.html

See Also

as.Date, strptime, WqData-class

Examples

# Create new WqData object from sfbay data. First combine date and time
# into a single string after making sure that all times have 4 digits.
sfb <- transform(sfbay, time = substring(10000 + time, 2, 5))
sfb <- transform(sfb, time = paste(date, time, sep = ' '))
sfb <- wqData(sfb, 2:4, 5:12, site.order = TRUE, type = "wide",
    time.format = "%m/%d/%Y %H%M")

head(sfb)

# If time of day were not required, then the following would suffice:
sfb <- wqData(sfbay, c(1,3,4), 5:12, site.order = TRUE, type = "wide", 
  time.format = "%m/%d/%Y")

head(sfb)
summary(sfb)