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Re: STANDARD DEVIATON [message #21054 is a reply to message #20952]

Fri, 04 August 2000 00:00

Ben Marriage
Messages: 12
Registered: June 1999

Junior Member

Benno Puetz wrote:
>
> Alex Schuster wrote:
>
>> For some 3x3 pixels x_i (and a mean of x_mean), the standard deviation
>> is
>> s = 1/9 * sqrt( sum( (x_i-x_mean)^2 ) ). img=img-smooth(img,3) does the
>> inner subtraction of the x_means,
>
> unfortunately, that's not quite true (except for special cases) since the x_i
> get only their respective mean subtracted, not the center pixel mean. I came
> up with the same solution initially but it would not stand the test ...
>
> haven't had a better idea since :(
>

I think that's what I discovered too - hence the question to the NG.

I'll try and have another think about it.

Thanks,
Ben

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[Message index]

		STANDARD DEVIATON By: Ben Marriage on Tue, 01 August 2000 00:00
		Re: STANDARD DEVIATON By: Struan Gray on Fri, 04 August 2000 00:00
		Re: STANDARD DEVIATON By: Struan Gray on Fri, 04 August 2000 00:00
		Re: STANDARD DEVIATON By: Struan Gray on Fri, 04 August 2000 00:00
		Re: STANDARD DEVIATON By: Ben Marriage on Fri, 04 August 2000 00:00
		Re: STANDARD DEVIATON By: Ben Marriage on Fri, 04 August 2000 00:00
		Re: STANDARD DEVIATON By: Ben Marriage on Mon, 14 August 2000 00:00

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