Editing Binary logarithm (section)

===Bioinformatics===
[[File:Mouse cdna microarray.jpg|thumb|upright=1|A [[microarray]] for approximately 8700 genes. The expression rates of these genes are compared using binary logarithms.]]
In [[bioinformatics]], [[microarray]]s are used to measure how strongly different genes are expressed in a sample of biological material. Different rates of expression of a gene are often compared by using the binary logarithm of the ratio of expression rates: the log ratio of two expression rates is defined as the binary logarithm of the ratio of the two rates. Binary logarithms allow for a convenient comparison of expression rates: a doubled expression rate can be described by a log ratio of {{math|1}}, a halved expression rate can be described by a log ratio of {{math|−1}}, and an unchanged expression rate can be described by a log ratio of zero, for instance.<ref>{{citation|title=Microarray Gene Expression Data Analysis: A Beginner's Guide|first1=Helen|last1=Causton|first2=John|last2=Quackenbush|first3=Alvis|last3=Brazma|publisher=John Wiley & Sons|year=2009|isbn=978-1-4443-1156-3|pages=49–50|url=https://books.google.com/books?id=bg6D_7mdG70C&pg=PA49}}.</ref>

Data points obtained in this way are often visualized as a [[scatterplot]] in which one or both of the coordinate axes are binary logarithms of intensity ratios, or in visualizations such as the [[MA plot]] and [[RA plot]] that rotate and scale these log ratio scatterplots.<ref>{{citation|title=Computational and Statistical Methods for Protein Quantification by Mass Spectrometry|first1=Ingvar|last1=Eidhammer|first2=Harald|last2=Barsnes|first3=Geir Egil|last3=Eide|first4=Lennart|last4=Martens|publisher=John Wiley & Sons|year=2012|isbn=978-1-118-49378-6|page=105|url=https://books.google.com/books?id=3Z3VbhLz6pMC&pg=PA105}}.</ref>