[R] summation equation whose numerator has subscript

[Jeff Newmiller]

I cannot understand that summation at all,  much less translate it to R. Do you have an original citation for this thing? 

As for putting subscripts in parameter lists,  that is not going to happen. You have to accept that the code that calls your function needs to do any necessary subscripting before it gives that piece to your function. Keep in mind that apply functions do this by their nature without the mess of specifying it yourself. If you know that the automatic subscripting that sapply does is not going to get the result you want then don't use that function. 
-- 
Sent from my phone. Please excuse my brevity.

On November 30, 2015 1:20:34 PM PST, Sherouk Moawad via R-help <r-help at r-project.org> wrote:
>Dear R experts 
>Please do you have any idea about how this summation can be written in
>R(the equation can be viewed in the following link): 
>http://s16.postimg.org/or2km30ph/equation.jpg 
>
>I've tried out out this code but it gave me error for writing brackets
>in function of summation:
>
>>>> 
>x=matrix(c(6,2,1),3,1) 
>
>for (l in 1:3){ 
>sum(sapply(1:3, function(j[l]){if(l>1){sum(sapply(1:j[l-1],
>function(j[l]){x[j[l]]*(j[l]<j[l-1])}))}}))}>>>Thank you
>
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