# Grabbing Indexes of a certain standard deviation

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## Grabbing Indexes of a certain standard deviation

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## Re: Grabbing Indexes of a certain standard deviation

 I wrote a little function called first() to help with situations like this.  It returns a 1 every time an element of a vector is different from the previous element, and a 0 otherwise. first <- function(x) {     L <- length(x)     c(1, 1-(x[-1]==x[-L]))     } sd <- 1 residuals <- c(1, 2.1, 3, 4, 3, 1, 0, -4, -1) # logical, indicating if the residual exceeds 2 standard deviations exceed <- abs(residuals) > (2*sd) # indices of the first exceeding residual of a series which(first(exceed) & exceed) Jean gcm <[hidden email]> wrote on 07/12/2012 11:07:49 AM: > I have a graph of residuals and I am attempting to get a list of the indexes > of each time the residual is greater than 2 standard deviations or less than > -2 standard deviations, but only the first point of the section. And then > I'd also need the first point where the point returns to the range between > +/- 2 standard deviations. > So basically if my standard deviation=1 and my residuals=c(1, 2.1, 3, 4, 3, > 1, 0, -4, -1) I want it to grab the second number, where it exceeds 2 > standard deviations and the 6th where it returns to less than 2 standard > deviations. Also, it would grab -4 (or residuals[ 8]) and -1 (residuals[9])         [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## RE: Grabbing Indexes of a certain standard deviation

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## Re: Grabbing Indexes of a certain standard deviation

 residuals[abs(residuals) > (2*sd)] gcm <[hidden email]> wrote on 07/16/2012 07:07:31 AM: > Jean, how would you modify your function to grab all the selected > and not just the first? > Thank you so much! > > From: Jean V Adams [via R] [ mailto:[hidden email]] > Sent: Thursday, July 12, 2012 4:59 PM > To: Lauren Vogric > Subject: Re: Grabbing Indexes of a certain standard deviation > > I wrote a little function called first() to help with situations like > this.  It returns a 1 every time an element of a vector is different from > the previous element, and a 0 otherwise. > > first <- function(x) { >     L <- length(x) >     c(1, 1-(x[-1]==x[-L])) >     } > > sd <- 1 > residuals <- c(1, 2.1, 3, 4, 3, 1, 0, -4, -1) > # logical, indicating if the residual exceeds 2 standard deviations > exceed <- abs(residuals) > (2*sd) > # indices of the first exceeding residual of a series > which(first(exceed) & exceed) > > Jean > > > gcm <[hidden email]> > wrote on 07/12/2012 11:07:49 AM: > > > I have a graph of residuals and I am attempting to get a list of the > indexes > > of each time the residual is greater than 2 standard deviations or less > than > > -2 standard deviations, but only the first point of the section. And > then > > I'd also need the first point where the point returns to the range > between > > +/- 2 standard deviations. > > So basically if my standard deviation=1 and my residuals=c(1, 2.1, 3, 4, > 3, > > 1, 0, -4, -1) I want it to grab the second number, where it exceeds 2 > > standard deviations and the 6th where it returns to less than 2 standard > > deviations. Also, it would grab -4 (or residuals[ 8]) and -1 > (residuals[9])         [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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