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Subject: Re: expectated value
Date: Tue, 15 Jan 2013 18:47:14 +0000 (UTC)
Organization: Istanbul Technical University
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"Torsten" wrote in message <kd3rgg$d1h$1@newscl01ah.mathworks.com>...
> "maryam" wrote in message <kd3p99$3qu$1@newscl01ah.mathworks.com>...
> > "Nasser M. Abbasi" wrote in message <kd34i6$p21$1@speranza.aioe.org>...
> > > On 01/15/2013 01:47 AM, maryam wrote:
> > > > Dear friens
> > > > I would like calculate the expectated value (E(.)) of a 1-by-1000 matrix
> > > > {E(x)=sigma x*f(x)}
> > > > how do I that?
> > > 
> > > Apply the definition of expected value?
> > > 
> > > when you are not sure how to do something, always look up
> > > the definition and go from there.
> > > 
> > > http://en.wikipedia.org/wiki/Expected_value
> > > 
> > > If you have problem with implementing the defintion, then show
> > > what you tried and where you are having problem.
> > > 
> > > good luck,
> > > 
> > > --Nasser
> > --------------------
> > I know the the definition of expected value but I cant implement it.
> > assume a  1-by-n arbitrary matrix, what's its matlab code?
> > thanks 
> 
> A row of numbers does not have an expected value.
> What you probably mean is an estimator for the expected value
> of the random variable which produced the row of numbers. 
> Usually one takes 
> mean(A,2) 
> for this where A is your 1xn - matrix.
> 
> Best wishes
> Torsten.
-----------------------------
Dear Torsten
thanks your reply
In the part of my thesis I obtain a vector of random variables that is  I=1xn - matrix.
then I must to calculate "contrast (I)" , the definition of contrast is contrast(x)=E(x^2)/(E(x))^2
 and E(.) denoted the expectation operator.
how could I calculate contrast (I)?
thank you very much