On 12-06-2013, at 04:53, Abdul Rahman bin Kassim (Dr.) <rahmank at
frim.gov.my> wrote:
>
> Dear R-User,
>
> Appreciate any helps. It looks simple, but I don't have a clue.
>
> Given that I have a dataframe of tree population with three variables:
>
> sp=species ,
> d0=initial_size
> grow=growth increment from initial size per year
>
> How can I calculate the future growth increment of each tree for the next
3 years.
>
> The following Rscript was written,
>
> #----------
> a0 <- data.frame(d0=seq(5,50,5) , sp=gl(2,5,10),
> grow=rep(0.5,10))
> a2<- list()
> for( i in 1:3){
> a1 <- a0$d0+a0$grow
> a2[[i]] <- cbind(sp=a0$sp,d0=a1+i,yr=i)
> }
> as.data.frame(do.call(cbind,a2))
>
>> as.data.frame(do.call(cbind,a2))
> sp d0 yr sp d0 yr sp d0 yr
> 1 1 6.5 1 1 7.5 2 1 8.5 3
> 2 1 11.5 1 1 12.5 2 1 13.5 3
> 3 1 16.5 1 1 17.5 2 1 18.5 3
> 4 1 21.5 1 1 22.5 2 1 23.5 3
> 5 1 26.5 1 1 27.5 2 1 28.5 3
> 6 2 31.5 1 2 32.5 2 2 33.5 3
> 7 2 36.5 1 2 37.5 2 2 38.5 3
> 8 2 41.5 1 2 42.5 2 2 43.5 3
> 9 2 46.5 1 2 47.5 2 2 48.5 3
> 10 2 51.5 1 2 52.5 2 2 53.5 3
>
> #-----
>
> but the results did not produce the expected future d0. I think its my R
script "d0=a1+i" in the " a2[[i]] <-
cbind(sp=a0$sp,d0=a1+i,yr=i)". Interested to know the correct way of
writing the repeated loops in R.
>
> The expected results is:
>
> sp d0 yr sp d0 yr sp d0 yr
> 1 1 6.5 1 1 7.0 2 1 7.5 3
> 2 1 11.5 1 1 12.0 2 1 12.5 3
> 3 1 16.5 1 1 17.0 2 1 17.5 3
> 4 1 21.5 1 1 22.0 2 1 22.5 3
> 5 1 26.5 1 1 27.0 2 1 27.5 3
> 6 2 31.5 1 2 32.0 2 2 32.5 3
> 7 2 36.5 1 2 37.0 2 2 37.5 3
> 8 2 41.5 1 2 42.0 2 2 42.5 3
> 9 2 46.5 1 2 47.0 2 2 47.5 3
> 10 2 51.5 1 2 52.0 2 2 52.5 3
>
Why is the expression a1 <- a0$d0+a0$grow inside the for loop?
It doesn't depend on i.
I don't understand your expected result.
Fpr species 1 the initial value in column d0 is 5. I assume that this is in year
0.
So with a growth increment of .5 in year 1 I would expect d0 to be 5.5, in year
2it is 6 and in year 3 it would be 6.5.
So see if this does what you seem to want (and remove the redundant expression
for a1)
a3<- list()
for( i in 1:3){
a3[[i]] <- cbind(sp=a0$sp,d0=a0$d0+i*a0$grow,yr=i)
}
as.data.frame(do.call(cbind,a3))
# sp d0 yr sp d0 yr sp d0 yr
# 1 1 5.5 1 1 6 2 1 6.5 3
# 2 1 10.5 1 1 11 2 1 11.5 3
# 3 1 15.5 1 1 16 2 1 16.5 3
# 4 1 20.5 1 1 21 2 1 21.5 3
# 5 1 25.5 1 1 26 2 1 26.5 3
# 6 2 30.5 1 2 31 2 2 31.5 3
# 7 2 35.5 1 2 36 2 2 36.5 3
# 8 2 40.5 1 2 41 2 2 41.5 3
# 9 2 45.5 1 2 46 2 2 46.5 3
# 10 2 50.5 1 2 51 2 2 51.5 3
Berend