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From |
Matthew White <mwhite@poverty-action.org> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Accumulated mean and standard deviation |

Date |
Sun, 8 Jan 2012 11:35:48 -0500 |

Hi Pedro, For the mean, you can use -sum()-, which calculates the running sum: generate mean = sum(x) / _n The SD is harder. Here's one attempt. It was faster for me than using -egen sd()- in a loop: generate sd = . generate touse = 0 forvalues i = 1/`=_N' { quietly replace touse = 1 in `i' quietly summarize x if touse quietly replace sd = r(sd) in `i' } Best, Matt On Sun, Jan 8, 2012 at 10:50 AM, Pedro Nakashima <nakashimapedrolist@gmail.com> wrote: > Hi everybody > > I need to replicate the following data: > > clear* > > input x mean sd > 2 2 . > 4 3 1.4142 > 1 2.33 1.5275 > 3 2.55 1.2909 > end > > The variables mean and sd are like a mix of sum() and egen functions. > > For the variable "mean", in each observation j, its entry is the mean > of the values of the variable "x" from observation 1 up to observation > j. > For example: > 2 is the mean of 2 > 3 is the mean of 4 and 2 > 2.33 is the mean of 1, 4 and 2 > 2.55 is the mean of 3, 1, 4 and 2 > > The same is true for the variable sd, but here we consider the > standard deviation. > > Does anyone know how to solve this problem? > > Many thanks, > Pedro Nakashima. > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ -- Matthew White Data Coordinator Innovations for Poverty Action 101 Whitney Avenue, New Haven, CT 06510 USA +1 434-305-9861 www.poverty-action.org * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Accumulated mean and standard deviation***From:*Pedro Nakashima <nakashimapedrolist@gmail.com>

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