[R-sig-teaching] Calculation with R

[Martin Maechler]

>>>>> Randall Pruim <rpruim at calvin.edu>
>>>>>     on Thu, 21 Jul 2016 15:32:00 +0000 writes:

    > This isn’t really a teaching question, 

Yes, indeed this is NOT  about 'teaching R'  or
'teaching with R', and hence not appropriate for the
R-SIG-teaching list.

Please, Steven Stoline, stop misusing this list for your questions about R.

There is the R-help mailing list for that, and other fora,
such as Stackoverflow, see

https://www.r-project.org/posting-guide.html    and also
https://www.r-project.org/mail.html

Martin Maechler
(ETH Zurich / R Core)

    > but for your particular case IIYC, just multiply the squared quantity by data[,2] before summing.  For more general cases, take a look at ifelse().
    >> On Jul 21, 2016, at 11:20 AM, Steven Stoline <sstoline at gmail.com> wrote:
    >> 
    >> Dear All: good morning
    >> 
    >> I do need your help how to do the following calculation:
    >> 
    >> Assume we have a matrix 13x2 (say). Two columns named dataval and index
    >> 
    >> dataval index
    >> 20 1
    >> 11 0
    >> 34 0
    >> 54 1
    >> 76 1
    >> 76 0
    >> 61 1
    >> 88 1
    >> 91 0
    >> 11 0
    >> 23 1
    >> 45 1
    >> 53 0
    >> 
    >> data<-matrix(c(20,11,34,54,76,76,61,88,91,11,23,45,53,1,0,0,1,1,0,1,1,0,0,1,1,0),13,2)
    >> 
    >> data
    >> 
    >> I need to perform the calculation:
    >> 
    >> for a = 7 (say)
    >> 
    >> sum((data[ ,1] - a)^2)
    >> 
    >> only for index = data[ ,2] = 1
    >> 
    >> 
    >> I am expecting the result to be equal to:
    >> 
    >> (20-7)^2 + (54-7)^2+(76-7)^2+(61-7)^2+(88-7)^2+(23-7)^2+(45-7)^2 = 18316
    >> 
    >> 
    >> Any helps will be highly appreciated.
    >> 
    >> 
    >> with many thanks
    >> steve
    >> -------------------------
    >> Steven M. Stoline
    >> 1123 Forest Avenue
    >> Portland, ME 04112
    >> sstoline at gmail.com
    >> 
    >> [[alternative HTML version deleted]]
    >> 
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