bReeze (version 0.3-2)

monthStats: Calculation of monthly statistics

Description

Calculates monthly statistics.

Usage

monthStats(mast, set, signal="v.avg", 
  fun=c("mean", "median", "min", "max", "sd"), subset, 
  digits=3, print=TRUE)
ms(mast, set, signal="v.avg", 
  fun=c("mean", "median", "min", "max", "sd"), subset, 
  digits=3, print=TRUE)

Arguments

mast

Met mast object created by createMast.

set

Set used for calculation specified as set number or set name. If missing, the calculation is carried out for all datasets that contain the specified signal.

signal

The signal to be used, as string value. Default is "v.avg".

fun

Statistical function, as string value -- one of "mean" (arithmetic mean), "median", "min" (minimum), "max" (maximum) or "sd" (standard deviation).

subset

Optional start and end time stamp for a data subset, as string vector c(start, end). The time stamps format shall follow the rules of ISO 8601 international standard, e.g. "2012-08-08 22:55:00".

digits

Number of decimal places to be used for results as numeric value. Default is 3.

print

If TRUE, results are printed directly.

Value

• Returns a list of data frames (one for each dataset) containing monthly, annual and total statistics of the specified signal.

encoding

UTF-8

Details

monthStats calculates statistics of valid data for each month and year in the measurement period. Usually this function is used for the calculation of average wind speeds. Means strongly depend on the measurement period and the number of samples. One important requirement for a reliable wind assessment is a measurement period covering the full seasonal cycle of variations. A typical bias is a measurement limited to winter months, which usually results in overestimated wind speeds.

References

Brower, M., Marcus, M., Taylor, M., Bernadett, D., Filippelli, M., Beaucage, P., Hale, E., Elsholz, K., Doane, J., Eberhard, M., Tensen, J., Ryan, D. (2010) Wind Resource Assessment Handbook. http://www.renewablenrgsystems.com/TechSupport/~/media/Files/PDFs/wind_resource_handbook.ashx

See Also

createMast, plotMonthStats, printObject

Examples

# load and prepare data
data(winddata)
set40 <- createSet(height=40, v.avg=winddata[,2], v.max=winddata[,3])
set30 <- createSet(height=30, v.avg=winddata[,6], v.max=winddata[,7])
set20 <- createSet(height=20, v.avg=winddata[,10])
ts <- formatTS(time.stamp=winddata[,1])
neubuerg <- createMast(time.stamp=ts, set40, set30, set20)
neubuerg <- clean(mast=neubuerg)

# calculate monthly means
neubuerg.stats <- monthStats(mast=neubuerg)

# calculate monthly means for one dataset
monthStats(mast=neubuerg, set=1)
monthStats(mast=neubuerg, set="set1")	# same as above

# calculate monthly means for another signal
monthStats(mast=neubuerg, signal="v.max")

# calculate monthly median, min, max and standard deviation
monthStats(mast=neubuerg, fun="median")
monthStats(mast=neubuerg, fun="min")
monthStats(mast=neubuerg, fun="max")
monthStats(mast=neubuerg, fun="sd")

# data subsets
monthStats(mast=neubuerg, 
  subset=c("2009-12-01 00:10:00", "2009-12-31 23:50:00"))
monthStats(mast=neubuerg, 
  subset=c("2010-01-01 00:10:00", NA)) # just 'start' time stamp
monthStats(mast=neubuerg, 
  subset=c(NA, "2009-12-31 23:50:00")) # just 'end' time stamp

# change number of digits and hide results
monthStats(mast=neubuerg, digits=2)
monthStats(mast=neubuerg, print=FALSE)