Greetings List,
I'm having some trouble with the use of the names function in a formula. Below is an example of something that works (i.e first line), and the second line is the same formula which doesn't. I want to be able to reference the column of the dataC table so I can run the variogram iteratively with a loop.
> v<-variogram(A1~1,loc=~x+y, dataC)
> v<-variogram(names(dataC[3])~1,loc=~x+y, dataC)
Error in model.frame(formula, rownames, variables, varnames, extras, extranames, :
invalid variable type
Where dataC looks like:
x y A1 A2 A3
1 514030 4793587 0.0 7.9 0.1
2 517995 4792516 5.8 5.1 0.0
3 514232 4792210 0.0 6.5 0.0
I though initially that it might need some escape character if quotes are added, and tried the following, but it looks ok.
> names(dataC[3])
[1] "A1"
> mode(names(dataC[3]))
[1] "character"
> v<-variogram(as.character(names(dataC[3]))~1,loc=~x+y, dataC)
Error in model.frame(formula, rownames, variables, varnames, extras, extranames, :
invalid variable type
> v<-variogram(as.formula((names(dataC[3]))~1),loc=~x+y, dataC)
Error in model.frame(formula, rownames, variables, varnames, extras, extranames, :
invalid variable type
I'd greatly appreciate any suggestions for fixing this.
Thanks again,
femke
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