Bluebit Software Support Forum / Technical Support and Help / Matrix ActiveX Component / column variance / Latest PostsInstantForum.NET v4.1.4Bluebit Software Support Forumhttp://www.bluebit.gr/forum/support@bluebit.grThu, 09 Sep 2010 13:10:11 GMT20<link>http://www.bluebit.gr/forum/Topic138-1-1.aspx</link><description>thanks :)</description><pubDate>Mon, 27 Nov 2006 08:08:58 GMT</pubDate><dc:creator>zicon</dc:creator></item><item><title /><link>http://www.bluebit.gr/forum/Topic138-1-1.aspx</link><description>Sum( (x-mean)^2 ) = Sum( x^2 ) - 2*Sum(x)*mean + N*mean^2 = Sum(x^2) - 2 * Sun(x)* ( Sum(x)/N ) + N *(Sum(x)^2/N^2) == Sum(x^2) - Sum(x)^2 / NYou can get Sum(x) using ColSum method</description><pubDate>Fri, 24 Nov 2006 09:14:11 GMT</pubDate><dc:creator>Trifon</dc:creator></item><item><title /><link>http://www.bluebit.gr/forum/Topic138-1-1.aspx</link><description>I cant use that as that will not give me the variance as it is the sum of the x^2 and not the sum of (x-mean)^2I can do it the long way by looping through but just wondered if there was a quicker command</description><pubDate>Fri, 24 Nov 2006 08:53:24 GMT</pubDate><dc:creator>zicon</dc:creator></item><item><title /><link>http://www.bluebit.gr/forum/Topic138-1-1.aspx</link><description>Using the ColsDotProduct(col, col) you can get Sum(x^2) and then you divide by N or N-1 where N is the number of rows.</description><pubDate>Fri, 24 Nov 2006 05:22:34 GMT</pubDate><dc:creator>Trifon</dc:creator></item><item><title>column variancehttp://www.bluebit.gr/forum/Topic138-1-1.aspxwhat is the best way to get the variance of a column in a matrix?Fri, 24 Nov 2006 04:26:26 GMTzicon