Sounds good to me. I updated the page.
-- Raul On Mon, Jun 13, 2016 at 12:32 PM, Martin Kreuzer <[email protected]> wrote: > Hi all - > > While browsing the J NuVoc page I accidentally stumbled upon this example: > > URL: http://code.jsoftware.com/wiki/Vocabulary/ampdotco > > Under "Common Uses / 2. Compute standard deviation as the root-mean-square > of a list of differences from the mean value" > the example starts out with > > y =: 0 _2 1 2 NB. list of differences from the mean value > > This didn't look right to me as the sum of deviations does not result in > zero: > > +/ 0 _2 1 2 > 1 > > So I made up an example myself: > > obs=. 5 2 6 7 NB. observed data > amean=. +/ % # NB. arithmetic mean > dev=. ] - amean NB. deviation from mean value > dev obs > 0 _3 1 2 > > Comparing this result with the above (original set of deviations) > makes me think it might be a typo. > > The "mean deviation" (mean of absolute deviation values) would then be > > dmean=. amean @: | > dmean dev obs > 1.5 > > and the standard deviation (root-mean-square of deviation values) > > stddev=. amean &.: *: > stddev dev obs > 1.87083 > > Would somebody please have a look into that to check whether I'm utterly > wrong or not..? > > Thanks > -M > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
