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count (mex)

10 Jun 2004 (Updated 11 Jun 2004)

Counts the number elements in a specified vector or matrix that match a specified criteria.

File Information
Description	Given a vector or matix MATRIX, counts the number of times that the scalar X satisfy the (string) condition COND. The result is returned in the variable RES. the COND operators allowed are: ==, >=, <=, <, >, !=. The function is faster than SUM(MATRIX'COND'X) or LENGTH(FIND(MATRIX'COND'X)). A test script is provided to show the performances.
MATLAB release	MATLAB 6.5 (R13)
Other requirements	Tested on XP,R13

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Everyone's Tags	count, matrices, matrix, matrix manipulation, mex, utilities
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Comments and Ratings (1)
18 Feb 2006	Jos van der Geest	On my PC it is indeed about 4 times faster than the better known <sum> solution. However, it does not handle NaNs very well. count([1 2 NaN],1,'==') -> ans = 2 as opposed to sum([1 2 NaN]==1) -> ans = 1

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