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intprb_muvstepstart

Returns the starting values for the step-by-step (mean,variance) computation.

Calling Sequence

[ n , mu , v ] = intprb_muvstepstart ( )

Parameters

n :

a 1-by-1 matrix of floating point integersthe starting value of the number of values

mu :

a 1-by-1 matrix of doubles, the starting value of the mean

v :

a 1-by-1 matrix of doubles, the starting value of the sample variance, as the sum of squares divided by with n-1

Description

This routine is used in an algorithm which uses the step-by-step variance computation. It is designed to be used with intprb_muvstepupdate and intprb_muvstepstop. This function is useful in Monte-Carlo algorithms which do not keep track of all the function values, but only keep the last function value and update the mean and the variance dynamically.

Examples

// Compare our algorithm with the functions (mean,variance)
x = 1 : 10
[ n , mu , v ] = intprb_muvstepstart ( );
for i = 1 : 10
[ n , mu , v ] = intprb_muvstepupdate ( n , mu , v , x(i) );
end
[ n , mu , v ] = intprb_muvstepstop ( n , mu , v );
disp( [mean(x) mu ] )
disp( [variance(x) v ] )

Authors

Bibliography

Donald E. Knuth (1998). The Art of Computer Programming, volume 2: Seminumerical Algorithms, 3rd edn., p. 232. Boston: Addison-Wesley.

http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance


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