# [R] Odp: How to repeat "for" function?

Petr PIKAL petr.pikal at precheza.cz
Mon Feb 1 16:56:58 CET 2010

```Hi

r-help-bounces at r-project.org napsal dne 01.02.2010 14:51:17:

>
> Dear Users,
>
> I have one problem here, I tried many time and even read a few notes on
> writing function but still.....
>
>
> Can anyone help me on how to simplify Part B (please refer the
programming
> below), so that I don't have to repeat the calculation of "num" and "r"
?
>
>
>
> Thank you very much..every help is very much appreciated...
>
>
> ## Part A
> n=1400
> m=matrix(c(0,0,0,0),4,1)
> m2=matrix(c(0,2,0,0),4,1)
>
c4<-matrix(c(1.0,0.2,-0.5,0.3,0.2,1,0.2,-0.5,-0.5,0.2,1,0.2,0.3,-0.5,0.2,1),4,4,byrow=T)
> set.seed(428)
> X=mvrnorm(n,m2,c4)
> X.pca<-princomp(X)
>
> ##  Part B
> num1=rep(1:n)

is same as
num1 <- 1:n

> for(i in 1:n)num1[i]=pc%*%X[i,1]

If I understand what the above code does I am a bit surprised

pc is
> pc
 0.525037

for each number in cycle

X[i,1] is again a number

> X[1,1]
 0.7512862
> X[2,1]
 0.5020333
>

so it basically  results in

pc * X[,1]

which you can compute for all 4 columns by

kronecker(pc, X, "*")

But I wonder if this is what you really want.

Maybe you shall think it over again and try with some smaller manageable
subset lit

smallX <- X[1:5,]

do all your computation and if it does not produce what you want, specify
what you want.

Regards
Petr

> num2=rep(1:n)
> for(i in 1:n)num2[i]=pc%*%X[i,2]
> num3=rep(1:n)
> for(i in 1:n)num3[i]=pc%*%X[i,3]
> num4=rep(1:n)
> for(i in 1:n)num4[i]=pc%*%X[i,4]
>
> den=rep(1:n)
> for(i in 1:n)den[i]=pc%*%X[i,]
>
>
> r1=num1/den
> r2=num2/den
> r3=num3/den
> r4=num4/den
> MLAV=sum(r2>r1 & r2>r3 & r2>r4)
> MLAV
>
> Best regards,
> ayu
>
>
> --
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> tp1458806p1458806.html
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