# foldchange: Compute fold-change or convert between log-ratio and... In gtools: Various R Programming Tools

## Description

`foldchange` computes the fold change for two sets of values. `logratio2foldchange` converts values from log-ratios to fold changes. `foldchange2logratio` does the reverse.

## Usage

 ```1 2 3``` ```foldchange(num,denom) logratio2foldchange(logratio, base=2) foldchange2logratio(foldchange, base=2) ```

## Arguments

 `num,denom` vector/matrix of numeric values `logratio` vector/matrix of log-ratio values `foldchange` vector/matrix of fold-change values `base` Exponential base for the log-ratio.

## Details

Fold changes are commonly used in the biological sciences as a mechanism for comparing the relative size of two measurements. They are computed as: num/denom if num>denom, and as -denom/num otherwise.

Fold-changes have the advantage of ease of interpretation and symmetry about num=denom, but suffer from a discontinuty between -1 and 1, which can cause significant problems when performing data analysis. Consequently statisticians prefer to use log-ratios.

## Value

A vector or matrix of the same dimensions as the input containing the converted values.

## Author(s)

Gregory R. Warnes [email protected]

## Examples

 ```1 2 3 4 5 6``` ``` a <- 1:21 b <- 21:1 f <- foldchange(a,b) cbind(a,b,f) ```

gtools documentation built on June 26, 2018, 5:01 p.m.