Re: [eigen] Eigen appears to rock. |

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*To*: eigen@xxxxxxxxxxxxxxxxxxx*Subject*: Re: [eigen] Eigen appears to rock.*From*: "Thomas Vaughan" <tevaughan@xxxxxxxxx>*Date*: Fri, 22 Aug 2008 09:53:04 -0600*Dkim-signature*: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to :subject:in-reply-to:mime-version:content-type :content-transfer-encoding:content-disposition:references; bh=hcMgNdiwgoBhHzG+FS3pDTjAGQGkRoz9oIXSckDNKc0=; b=vNu5Dw/F9objRh1IxXiHbq7FCFmf5CBjwbLBvc3vytgXsDj4Pi7NfjtZWSms/60Zdd a+THfdKSP1se7JTc4A7ToBqjhv60zkCEWAPmHWBNx69HQ/KEDm7txuO0IOdZpk8KFZKH 21eWyZzp48ijrTKLMHWvVXXPg8B4nHvd0r6hY=*Domainkey-signature*: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:in-reply-to:mime-version :content-type:content-transfer-encoding:content-disposition :references; b=d2Kxi/evJX5irN4W22l8ox7m/hXAZ6574zHiadp2jeyH4aoZqVOIsHM9N04dofIrFX DzYxV1nT4BKrmd/Qm1P7+XqAxpdLR0KxzYRwUzlaQqgXzKuPsyXiUHVMTvvnptV14j72 UnaraGTpkRvYpzOio8Np/39J/xvgGSIFOrDCY=

On Fri, Aug 22, 2008 at 7:51 AM, Gael Guennebaud <gael.guennebaud@xxxxxxxxx> wrote: > > but what about more general weighted mean of a set of points: > > for(i) { > m += p[i] * weight[i]; > sumW += weight[i]; > } > m /= sumW; It seems that your p is really a displacement vector. Nevertheless, I agree that, for a large number of points, it is more expensive to do this: for(i) { m += (p[i]-po) * weight[i]; sumW += weight[i]; } m /= sumW; (though in some circumstances you might need to do this even in your scheme.) Overall this is probably the best argument why not to distinguish. In my work, I typically have only a few points and a large number of vectors. If you have huge numbers of points in the same coordinate system, it's way more efficient just to treat every point as if it were a displacement vector. You have largely convinced me. I think that the discussion is probably just about over. Thanks for your patience. -- Thomas E. Vaughan There are only two kinds of people; those who accept dogma and know it, and those who accept dogma and don't know it. - G.K. Chesterton

**Follow-Ups**:**Re: [eigen] Eigen appears to rock.***From:*Gael Guennebaud

**References**:**[eigen] Eigen appears to rock.***From:*Thomas Vaughan

**Re: [eigen] Eigen appears to rock.***From:*Thomas Vaughan

**Re: [eigen] Eigen appears to rock.***From:*Gael Guennebaud

**Re: [eigen] Eigen appears to rock.***From:*Konstantin Heil

**Re: [eigen] Eigen appears to rock.***From:*Gael Guennebaud

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