# var: Variance of frequency distribution table (numerical variable) In fdth: Frequency Distribution Tables, Histograms and Polygons

## Description

S3 methods for the variance of a `fdt`.
Useful to estimate the variance (when the real data vector is not known) from a previous `fdt`.

## Usage

 ``` 1 2 3 4 5 6 7 8 9 10 11 12``` ```## S3 generic var(x, ...) ## S3 methods: numerical ## Default S3 method: var(x, ...) ## S3 method for class 'fdt' var(x, ...) ## S3 method for class 'fdt.multiple' var(x, ...) ```

## Arguments

 `x` A `fdt` (simple or multiple) object. `...` Required to be generic.

## Details

`var.fdt` calculates the value of the variance based on a known formula. `var.fdt.multiple` calls `var.fdt`for each variable, that is, each column of the data.frame.

## Value

`var.fdt` returns a numeric vector containing the value of the median of the `fdt`. `median.fdt.multiple` returns a list, where each element is a numeric vector containing the value of the variance of the `fdt` for each variable.

## Author(s)

Jos<e9> Cl<e1>udio Faria
Enio G. Jelihovschi
Ivan B. Allaman

`sd.fdt`, `mean.fdt`.
 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17``` ```mdf <- data.frame(x=rnorm(1e2, 20, 2), y=rnorm(1e2, 30, 3), z=rnorm(1e2, 40, 4)) head(mdf) apply(mdf, 2, var) var(fdt(mdf)) ```