
Dear R-User,

Appreciate any helps.

Given that I have a dataframe of tree population with three variable:

sp=species ,
d0=initial_size
grow=growth increment from initial size per year

How can I calculate the future growth of each tree  for the next 10 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

Thanking you in advance for any helps.

Abd Rahman



Note: the fixed grow value of 0.5 is only an example. The real data may use growth equation to calculate the increment in a single year.

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