[R-sig-teaching] Calculation with R

[Randall Pruim]

This isn’t really a teaching question, 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
> 
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