Now I have the forest plot data with x, y locations, and I measured the DBH for every indivicuals.

The data looks like that:
x=runif(100,0,100)
y=runif(100,0,100)
dbh=runif(100,1,100)
rdata=data.frame(x,y,dbh)
> rdata[1:5,]
           x         y      dbh
1 99.5354145  1.412844 34.10112
2  0.8259361 87.737036 39.12914
3  6.5678613 65.699032 22.55990
4 67.2987881 72.053877 45.83978
5  2.2491372 23.622898 68.77065

My question is: How can I plot the grid (25×25,5×5,...) figure by DBH?
Can you introduce a simply method to do it by R language? I know that it can be done very easy by the software ArcGis.

　　　　
　　　　
　　　　
　　　　


Thanks very much.

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