# px: Percentile Ranks and Cumulative Frequencies In equate: Observed-Score Linking and Equating

## Description

These functions compute percentile ranks and cumulative frequency distributions for frequency tables.

## Usage

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15``` ```px(x, ...) ## Default S3 method: px(x, y, ys, ...) ## S3 method for class 'freqtab' px(x, margin = 1, y, ymargin = 1, ...) fx(x, ...) ## Default S3 method: fx(x, ...) ## S3 method for class 'freqtab' fx(x, margin = 1, ...) ```

## Arguments

 `x` either a vector of counts, or an object of class “`freqtab`” from which counts will be taken. `...` further arguments passed to or from other methods. `y` an object of class “`freqtab`” when `x` is as well, otherwise, a vector or `data.frame` of counts. See below for details. `ys` vector specifying the `y` score scale, when it is not contained in the first column of `y`. If `y` can be converted to a `data.frame`, it is assumed to be univariate with the first column containing the score scale and the second containing the counts. `margin, ymargin` integers specifying the margins for which frequencies or percentile ranks will be returned. `margin` applies to `x` and `ymargin` to `y`.

## Details

These functions compute percentile ranks and cumulative frequencies for a univariate distribution, and percentile ranks from one univariate distribution (`x`) corresponding to score values in another (`y`).

## Value

A vector is returned containing either percentile ranks or cumulative frequencies with length equal to `length(x)`.

## Author(s)

Anthony Albano [email protected]

`freqtab`
 ``` 1 2 3 4 5 6 7 8 9 10 11``` ```x <- as.freqtab(ACTmath[, 1:2], drop = TRUE) y <- as.freqtab(ACTmath[, c(1, 3)], drop = TRUE) # Percentile ranks for the x scale round(px(x), 3) # Percentile ranks in y for x each score round(px(x, y = y), 3) # Cumulative frequency distribution for x round(fx(x), 3) ```