High, Low, Open, and Close Calculation
Calculates the high, low, first, and last elements of a vector.
Especially useful for financial trading data in conjunction with
the aggregateSeries function.
a vector for which to calculate high, low, open, and close.
returns a vector with four elements:
|the maximum value in x.|
|the minimum value in x.|
|the first value of x.|
|the last value of x.|
can be an array, but dimensions are ignored.
x <- c(5, 2, 3, 6, 3, 2, 1, 7, 1)