| foldchange {gtools} | R Documentation |
Compute fold-change or convert between log-ratio and fold-change.
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
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: \frac{num}{denom} if
num>denom, and as \frac{-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 greg@warnes.net
Examples
a <- 1:21
b <- 21:1
f <- foldchange(a,b)
cbind(a,b,f)