Hi,

I'm trying to plot an equation in two variables to get a feel
for sensitivity to its parameters. I've run expand.grid to get made-up
vectors of the combinations of the two independent variables, and am trying
to plot the output of the dependent, M, against both the dependent in a 3d
space.

 t <- 0:100
 DBH <- 10:100
 TxDBH<-expand.grid(t,DBH)
 time<-TxDBH[,1]
 dbh<-TxDBH[,2]
 M <- 4000*(1-exp(-time*(1.104-(0.67*0.7)-0.163*log(dbh))^2))

I've tried wireframe(M~t|DBH, data=TxDBH)
 wireframe(M~time|dbh, data=M)
 wireframe(M~time|dbh)
 also the above model specifications using cloud.

but

 I get the following errors:
 Error in latticeParseFormula(formula, data, dimension = 3, subset = subset,
 :
  invalid model
Error in eval(substitute(groups), data, environment(formula)) :
  numeric 'envir' arg not of length one

any advice much appreciated.

*Ben *

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