Re: [R] sapply or apply

From: Joshua Wiley <jwiley.psych_at_gmail.com>
Date: Wed, 16 Jun 2010 23:30:40 -0700

Hello Roslina,

Maybe it is just me, but I have difficulty picking apart what you are trying to do because, the data have the same names as the arguments in your functions, and when you create the function term(), you have two sets of arguments (for term() and for gam_sum() ) that have the same names in addition to data with the same names. You also rely on the arguments' locations rather than explicitly stating their names. My guess is that you are having problems because sapply() is passing data from 'bt' to the first argument of gam_sum(), (which is named 'alp' ), so you *might* not be using the data you think you are in the arguments you think you are.

At any rate, I can tell you what is happening right now with term(). It is calling gam_sum() for each individual element of 'bt' like so:

gam_sum(bt[1],alp,bt_min,1)
gam_sum(bt[2],alp,bt_min,1)
gam_sum(bt[3],alp,bt_min,1)
gam_sum(bt[4],alp,bt_min,1)

and taking the sum of all of these. Note that since the data 'alp' has 4 elements, gam_sum() also puts out 4 elements, for each element of the data 'bt' .

Best regards,

Josh

On Wed, Jun 16, 2010 at 5:21 PM, Roslina Zakaria <zroslina_at_yahoo.com> wrote:
> Hi r-users,
>
> I have this code here :
>
> dt   <- winter_pos_sum
> bt   <- c(24.96874, 19.67861, 23.51001, 19.86868); round(bt,2)
>
> alp  <- c(2.724234, 3.914649, 3.229146, 3.120719); round(alp,2)
>
> bt_min  <- min(bt) ; bt_min
> p       <- alp_sum    ; p
> t  <- 50
> t1 <- t+1
>
>
> #first get the sum over the eigenvalues for a particular power i
> gam_sum <- function(alp,bt,bt_min,i) {alp*(1-bt_min/bt)^i}
> gam_sum(alp,bt,bt_min,1)
> 0.57718379+ 0.00000000+ 0.52625031+ 0.02985377 = 1.133288
>
>
>
> term   <- function(i,alp,bt,bt_min) {sum(sapply(bt,gam_sum , alp,bt_min,i))}
>> term (1,alp,bt,bt_min)
> [1] -1817.765
>
>
> I should get the value using term (1,alp,bt,bt_min)=1.133288. I have 4 values of beta and 4 values of alpha.
>
> Thank you so much for your help.
>
>
>
>        [[alternative HTML version deleted]]
>
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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>
>

-- 
Joshua Wiley
Ph.D. Student
Health Psychology
University of California, Los Angeles

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Received on Thu 17 Jun 2010 - 06:32:51 GMT

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