R: Selection for x,y coordinates with conditions - r

Question

I have some difficulties to solve a problem concerning the selection of values in a data frame. Here is the thing:
- I have a data frame containing these variables: x-coordinates, y-coordinates, diameter, G value, H value, Quality value, Ecological value. Each line corresponds to one individual (which are trees in this exercise)
I need to find the individual with the best quality value = this I can do it
But then, I have to find the second tree with a good quality value, which has to be in the 10 next meters of the reference tree (the one with the best quality value).
And this selection has to be made at every tree selected, every time 10 meters further!
this should bring me to a selection of x-y-coordinates, which are separated by 10 meters and represent good quality value.
Now, here is what I tried:
> kk<- function(x, y)
+ {
+ coordx<-data$x.Koordinate[data$Q==24] #I have looked before for the best quality value of the sample, which is 24
+ coordy<-data$y.Koordinate[data$Q==24]
+ x <- ifelse(data$x.Koordinate>coordx-11 & data$Q>15,data$x.Koordinate,0) #I choose that I did'nt wanted to have less than 15 of quality value
+ y<-ifelse(data$y.Koordinate>coordy-11 & data$Q>15,data$y.Koordinate,0)#-11 meters from the reference coordinates, the next tree selected has to be inbetween
+ return(c(x,y))
+ }
> kk(data$x.Koordinate, data$y.Koordinate)
[1] 0 0 0 0 0 205550 205550 0 205600 205600 0 0 0 0 0 0 0
[18] 604100 0 604150 604100 0
The problem here is that we can not clearly see the difference between the coordinates for x and the ones for y.
I tried this:
> kk<- function(x, y)
+ {
+ coordx<-data$x.Koordinate[data$Q==24]
+ coordy<-data$y.Koordinate[data$Q==24]
+ x <- ifelse(data$x.Koordinate>coordx-11 & data$Q>15,data$x.Koordinate," ")
+ y<-ifelse(data$y.Koordinate>coordy-11 & data$Q>15,data$y.Koordinate," ")
+ return(list(x,y))
+ }
> kk(data$x.Koordinate, data$y.Koordinate)
[[1]]
[1] " " " " " " " " " " "205550" "205550" " " "205600" "205600" " "
[[2]]
[1] " " " " " " " " " " " " "604100" " " "604150" "604100" " "
>
Where we can see better the two levels related to the x and y coordinates.
The first question is simple: Is it possible for this function to return the values in a form like x,y or x y ? (without any 0, or « », or space) Or should I use another R function to obtain this result?
The second question is complex: How can I say to R to repeat this function from the coordinates he finds in this first attempt, and for the whole data?

Answer 1

Thank you very much for your answer. It helps me a lot! The first part of my problem is solved, the second seems to have a bug somewhere... And I don't see clearly where the function says to R to go every 10 meters further (in fact, every 50 meters, according to my data, see below)...But thank you anyway, it's a good starter, I will continue my research on this problem :)
PS: I understand it is difficult without the data. Unfortunately, I cannot show them on the net. However, I can show you a part of it:
ID Bezeichnung x.Koordinate y.Koordinate Q N hdom V Mittelstamm Fi Ta Foe Lae ueN Bu Es Ei Ah ueL Struktur
1 10,809 62 205450 603950 8 1067 21 64 10 NA NA NA NA NA 100 NA NA NA NA NA
2 10,810 63 205450 604000 16 1333 22 128 12 NA NA NA NA NA 75 NA NA 25 NA NA
3 10,811 56 205500 604050 20 800 22 160 18 NA NA NA NA NA 60 NA NA NA 40 NA
4 10,812 55 205500 604000 12 1033 20 97 12 33 NA NA NA NA 67 NA NA NA NA NA
5 10,813 54 205500 603950 20 500 56 0 23 NA NA NA NA NA 100 NA NA NA NA NA
6 10,814 46 205550 604050 16 567 32 215 19 75 NA NA NA NA 25 NA NA NA NA NA
7 10,815 47 205550 604100 16 233 26 174 30 NA 25 NA NA NA 50 NA NA NA 25 NA
8 10,816 48 205550 604150 0 1167 16 0 0 NA NA NA NA NA NA NA NA NA NA NA
9 10,817 43 205600 604150 24 633 33 366 22 83 17 NA NA NA NA NA NA NA NA NA
10 10,818 42 205600 604100 16 1500 33 282 12 NA NA NA NA NA NA NA NA 75 25 NA
Here is the result with your answer for the second problem:
> Arbres<-kk(x.Koordinate, y.Koordinate, data=data)
> for (i in 1:length(Arbres[,1])
+ kk(Arbres(i,1),Arbres[i,2])
Error: unexpected symbol in:
"for (i in 1:length(Arbres[,1])
kk"
Sorry, I just rename it "Arbre"
Thanks again,
C.

Answer 2

It's a bit hard for me to try this out without your dataset, or a small example of it, but I think the following should work for your first question.
The first time you use the function you enter the x and y coordinate of the tree that has Quality 24 for x and y in your function
> kk<- function(x, y)
+ {
+ coordx<-x
+ coordy<-y
+ x1 <- ifelse(data$x.Koordinate>coordx-11 & data$Q>15,data$x.Koordinate,NA)
+ y1 <- ifelse(data$y.Koordinate>coordy-11 & data$Q>15,data$y.Koordinate,NA)
+ return(matrix(c(x1,y1),nrow=length(x1), ncol=2, dimnames=list(NULL, c("x","y"))))
+ }
That should give you a matrix with two columns corresponding to the x and y coordinates and a NA if the condition is not met.
The second question is more difficult because as your output already showed there are multiple trees that meet the criteria you've set. If you want all of these checked again you can use the output of your function in a loop. Something like this:
Tree1_friends<-kk(data$x.Koordinate[data$Q==24], data$y.Koordinate[data$Q==24])
for (i in 1:length(Tree1_friends[,1]))
print(kk(Tree1_friends[i,1],Tree1_friends[i,2]))
Note that this code only prints the result, but with some clever assignment strategy you can probably save them as well