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MyFisher33

3.0

3.0 | 2 ratings Rate this file 18 Downloads (last 30 days) File Size: 3.06 KB File ID: #15482

MyFisher33

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03 Jul 2007 (Updated )

A very compact routine to compute Fisher's exact test on a 3x3 matrix

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Description

Fisher's exact test of 3x3 contingency tables permits calculation of precise probabilities in situation where, as a consequence of small cell frequencies, the much more rapid normal approximation and chi-square calculations are liable to be inaccurate. The Fisher's exact test involves the computations of several factorials to obtain the probability of the observed and each of the more extreme tables. Factorials growth quickly, so it's necessary use logarithms of factorials. In Matlab this is very easy using the Gammaln function. The function uses preallocation and vectorization to speed-up the computations. Actually, the function also computes the mid-P correction to make the test less conservative.

MATLAB release MATLAB 7.3 (R2006b)
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Comments and Ratings (4)
12 Feb 2014 Giuseppe Cardillo

in my PC version it is correct. Bah! I uploaded it again

11 Feb 2014 Matthew

line 146: you must use "<=" not "<"

i.e., the line should read:

P=sum(np(np<=op));

(You want to sum across all probabilities that are less than or equal to the observed probability)

21 Jan 2013 Giuseppe Cardillo

Thank you. If you need fisher onto 2x3 matrix it is on FEX: http://www.mathworks.com/matlabcentral/fileexchange/15399

In any case, you can use Myfisher that it is able to manage any kind of matrix
http://www.mathworks.com/matlabcentral/fileexchange/26883

19 Jan 2013 Brani

Elegant, fast, clean and accurate. Thanks!
Why not have myfisher32.m? Best wishes, B.-

Updates
01 May 2008

waitbar added

27 Jun 2008

6-fold speed up using preallocation

12 Nov 2008

Changes in help section

26 Nov 2008

Improvements in table enumeration

23 Oct 2009

Actually, the function also computes the mid-P correction to make the test less conservative.

23 Dec 2009

Changes in description

12 Feb 2014

Minor bug correction

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