[GRASS-user] Natural breaks classification

[Luigi Ponti]

On 16/05/2012 21:10, Luigi Ponti wrote:
> On 16/05/2012 20:55, Salvatore Mellino wrote:
>> I'm trying but I receive an error.
>>
>> 1. In R I started the libraries spgarass6 and classInt
>> 2. I imported the DTM in R using           DTM<- 
>> readRAST6("DTM at mapset", ignore.stderr=TRUE)
>> 3. I used the command                DTM_class<- classIntervals(DTM, 
>> n=5, style="fisher")             and I received the error
>>
>> Error in classIntervals(DTM, n = 5, style = "fisher") :
>>    var is not numeric
>
> I do not recall exactly, but it may be that classIntervals does not 
> have a method for spatial data frames (i.e. the output of readRAST6). 
> One thing I would try to get the breaks anyway, is a regular R 
> data.frame, for example:
>
> DTM.df <- as.data.frame(DTM)
> DTM_class <- classIntervals(DTM.df, n=5, style="fisher")
>

I am replying to myself as I may have omitted part of the answer -- my 
apologies. Start the same way:

     DTM.df <- as.data.frame(DTM)

then get variable names:

     names(deltaYieldVector.df)

then use the variable of interest (altitude, I guess):

     DTM_class <- classIntervals(DTM.df$varOfInterest, n=5, style="fisher")

This should work; we were feeding a data.frame as input to 
classIntervals, whereas a variable is needed (e.g. one of the variables 
in the data.frame).

Let me know how it goes.

Kind regards,

Luigi