Hi all
I have a series of elevation transects between a list of pairwise locations.
This is not specifically a spatial question, but since it is a common
spatial task, i hope its okay.
head(Elevp)
Elevation ComboID From To
1 3408.080 1 262 138
2 3264.469 1 262 138
3 2904.685 1 262 138
4 2752.840 1 262 138
5 3408.080 2 262 129
6 3217.581 2 262 129
In the small section above, the first 'transect' has four points, and goes
from site 262 to site 138. I'm trying to find a way to get the total
elevation change over each transect. An abstract example is shown below.
> h
[1] 10 5 40 30 100 60
> g<-numeric()
> for(x in 1:(length(h)-1))
+ g[x]<-((abs(h[x+1]-h[x])))
> g
[1] 5 35 10 70 40
> sum(g)
[1] 160
to perform this over the entire database (1000's of comparisons)
agg<-aggregate(Elevp$Elevation,by=list(Elevp$From,Elevp$To),function(x)
how do i supply the former function, as a product that fits this setup?
Does a cumulative difference function exist? I'm not sure what to call it to
begin searching.
I appreciate the help.
Ben Weinstein
Ecology and Evolution
Stony Brook University
[[alternative HTML version deleted]]
_______________________________________________
R-sig-Geo mailing list
[email protected]
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
