Editing Cladogram (section)

====Consistency index====

The consistency index (CI) measures the consistency of a tree to a set of data – a measure of the minimum amount of homoplasy implied by the tree.<ref name="KLUGE, A. G 1969">{{cite journal | last1 = Kluge | first1 = A. G. | last2 = Farris | first2 = J. S. | year = 1969 | title = Quantitative Phyletics and the Evolution of Anurans | journal = Systematic Zoology | volume = 18 | issue = 1| pages = 1–32 | doi=10.2307/2412407| jstor = 2412407 }}</ref> It is calculated by counting the minimum number of changes in a dataset and dividing it by the actual number of changes needed for the cladogram.<ref name="KLUGE, A. G 1969"/>  A consistency index can also be calculated for an individual character ''i'', denoted c<sub>i</sub>.

Besides reflecting the amount of homoplasy, the metric also reflects the number of taxa in the dataset,<ref>{{cite journal | last1 = Archie | first1 = J. W. | last2 = Felsenstein | first2 = J. | year = 1993 | title = The Number of Evolutionary Steps on Random and Minimum Length Trees for Random Evolutionary Data | journal = Theoretical Population Biology | volume = 43 | pages = 52–79 | doi = 10.1006/tpbi.1993.1003 }}</ref> (to a lesser extent) the number of characters in a dataset,<ref name="ARCHIE, J. W 1989"/> the degree to which each character carries phylogenetic information,<ref name="Jennifer F p C">{{cite journal|doi=10.1111/j.1096-0031.2009.00270.x|title=A formula for maximum possible steps in multistate characters: Isolating matrix parameter effects on measures of evolutionary convergence|journal=Cladistics|volume=26|pages=98–102|year=2010|last1=Hoyal Cuthill|first1=Jennifer F.|last2=Braddy|first2=Simon J.|last3=Donoghue|first3=Philip C. J.|issue=1|pmid=34875753|s2cid=53320612|doi-access=free}}</ref> and the fashion in which additive characters are coded, rendering it unfit for purpose.<ref>{{cite journal | last1 = Sanderson | first1 = M. J. | last2 = Donoghue | first2 = M. J. | year = 1989 | title = Patterns of variations in levels of homoplasy | journal = Evolution | volume = 43 | issue = 8| pages = 1781–1795 | doi=10.2307/2409392| jstor = 2409392 | pmid = 28564338 }}</ref>

c<sub>i</sub> occupies a range from 1 to 1/[''n.taxa''/2] in binary characters with an even state distribution; its minimum value is larger when states are not evenly spread.<ref name="Jennifer F p C"/><ref name=Archie1996 /> In general, for a binary or non-binary character with <math>n.states</math>, c<sub>i</sub> occupies a range from 1 to <math>(n.states-1)/(n.taxa-\lceil n.taxa/n.states\rceil)</math>.<ref name="Jennifer F p C"/>