[R] if problem in function

[Tord Snall]

Dear all,

I have written a function for calculating the volume of a tree (=trad) or
snag (=högst). 

The included volume regreesion model includes ten parameter values, which
are tree species specific.

björk.formhöjd.pars is an object which includes the parameter values
(parameter set) for birch (=björk).

There is one row per tree in the data object.

> relev.kols[1:5, c("ObjektID", "CPYTradID", "tree.spec", "Diameter")]

  ObjektID CPYTradID tree.spec Diameter        
1     2101  2101.2.1     spruce        2 
2     2101  2101.2.2     spruce        7 
3     2101  2101.2.3     pine         29 
4     2101  2101.2.4     pine         38 
5     2101  2101.2.5     spruce        9 


My problem is that the function (below) does not choose new parameter set
for each row. Instead it now chooses (and uses) the spruce parameter set
for the whole data object (because there is spruce on the first row?).

Could someone please give a hint on what's wrong.

Thanks!

Sincerely,
Tord


relev.kols$vol<- ståvolfunk(relev.kols, tradhogst = "trad")

ståvolfunk<- function(datamat, tradhogst=c("trad", "högst")) 
                {   
    # first pick out correct parameter sets. They depend on tree species
                # if tree speciec is bjork (birch) -> choose
bjork.formhöjd.pars 
                # and bjork.höjd.pars as pars1 and pars2, respectively
#
                if(datamat$tree.spec == "Björk")  {  
                pars1<- björk.formhöjd.pars
                pars2<- björk.höjd.pars
                                                 }
                # if tree species is pine... 
                if( datamat$tree.spec == "pine" ) {  
                pars1<- pine.formhöjd.pars
                pars2<- pine.höjd.pars
                                                 }                         
                # spruce, lärk, en, obestämt barr, obestämt trad
                if(datamat$tree.spec == "spruce" | datamat$tree.spec ==
"Lärk" | datamat$tree.spec == "En" |
                    datamat$tree.spec == "Obestamt.barr" |
datamat$tree.spec == "Obestamt.trad")     {  
                pars1<- spruce.formhöjd.pars
                pars2<- spruce.höjd.pars
                pars2<- spruce.höjd.pars

                       }   
                # övrigt löv
                if(datamat$tree.spec != "Björk" & datamat$tree.spec !=
"pine" & datamat$tree.spec != "spruce" & 
                datamat$tree.spec != "Lärk" & datamat$tree.spec != "En" 
                & datamat$tree.spec != "Obestamt.barr" & datamat$tree.spec
!= "Obestamt.trad")  {  
                pars1<- övrlöv.formhöjd.pars
                pars2<- övrlöv.höjd.pars                       
                                             }      
    # then calculate volume for the tree (=trad) or snag (=högst)
                if(tradhogst == "trad"){ 
                           tradvol<- exp(Söderberg(datamat, pars1)) *
(datamat$Diameter)^2 * pi / 40000
                           return(tradvol)           
                                 }
                   
                if(tradhogst== "högst"){ 
                           # som cylinder om höjden är <3 m
                           if(datamat$LangdHojd<30){
                           högstvol<- ( (datamat$Diameter/2) /100) ^2 * pi
* (datamatris$LangdHojd/10) 
                                                    }
                           # och som kapat trad om höjden är högre 
                           else   
                           # först räknas ursprunglig höjd ut
                           urspr.tradhöjd<- exp(Söderberg(datamat,
pars2))/10 # omräknat till m
                           #höjdkvot
                           i<-  datamat$LangdHojd/10 /urspr.tradhöjd
                           # sedan ursprunglig volym
                           urspr.tradvol<- exp(Söderberg(datamat, pars1)) *
(datamat$Diameter)^2 * pi / 40000
                           # och så till sist högstubbens volym
                           högstvol<- urspr.tradvol* (2*i - i^2)
                           return(högstvol)           
                                  }  
                }



> relev.kols[1:5, c("ObjektID", "CPYTradID", "tree.spec", "Diameter", "vol")]
  ObjektID CPYTradID tree.spec Diameter          vol
1     2101  2101.2.1     spruce        2 0.0005896749
2     2101  2101.2.2     spruce        7 0.0164895879
3     2101  2101.2.3     pine       29 0.6840856989
4     2101  2101.2.4     pine       38 1.2839852602
5     2101  2101.2.5     spruce        9 0.0329307304