GroupedMedian: Calculate the Median of Already Grouped Data

In mrdwab/SOfun: Functions From Answers to R Questions on Stack Overflow

Description

Calculates the median of already grouped data given the interval ranges and the frequencies of each group.

Usage

GroupedMedian(frequencies, intervals, sep = NULL, trim = NULL)

Arguments

frequencies	A vector of frequencies.
intervals	A 2-row matrix with the same number of columns as the length of frequencies, with the first row being the lower class boundary, and the second row being the upper class boundary. Alternatively, intervals may be a column in your data.frame, and you may specify sep (and possibly, trim) to have the GroupedMedian function automatically create the required matrix for you.
sep	Optional. If the intervals are represented by a character vector with a character separating the interval ranges.
trim	Characters to trim from the vector before splitting. For example, if you are doing this on the output of cut (where, for some reason, you no longer have access to the original data), you can use the pre-set trim pattern "cut".

Value

A single numeric value representing the grouped median.

Author(s)

Ananda Mahto

References

http://stackoverflow.com/a/18931054/1270695

Examples

mydf <- structure(list(salary = c("1500-1600", "1600-1700", "1700-1800",
        "1800-1900", "1900-2000", "2000-2100", "2100-2200", "2200-2300",
        "2300-2400", "2400-2500"), number = c(110L, 180L, 320L, 460L,
        850L, 250L, 130L, 70L, 20L, 10L)), .Names = c("salary", "number"),
        class = "data.frame", row.names = c(NA, -10L))
mydf

GroupedMedian(frequencies = mydf$number, intervals = mydf$salary, sep = "-")

## Example with intervals manually specified
X <- rbind(c(1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400),
           c(1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500))

GroupedMedian(mydf$number, X)

set.seed(1)
x <- sample(100, 100, replace = TRUE)
y <- data.frame(table(cut(x, 10)))

GroupedMedian(y$Freq, y$Var1, sep = ",", trim = "cut")

mrdwab/SOfun documentation built on June 20, 2020, 6:15 p.m.