data$ID -> I always get a NULL

On Apr 20, 2009, at 4:33 AM, Grze? wrote:

This is my result:

class(data)

[1] "data.frame"

str(data)

'data.frame':	2193 obs. of  83 variables:
$ X.ID.                               : Factor w/ 2193 levels  
"'18201'",..:
1 2 3 4 5 6 7 8 9 10 ...
$ X.kod.                       : Factor w/ 20 levels  
"'01'","'02'",..: 1 1
1 1 1 1 1 1 1 1 ...
$ X.wiel.                         : int  7 7 7 7 7 7 7 8 8 8 ...
$ X.piech.                     : num  1 99.9 4 0.5 4 2 99.9 2 2  
99.9 ...
$ X.rodz.                       : int  NA 2 4 NA 4 2 2 3 2 NA ...

David Winsemius wrote:

On Apr 19, 2009, at 6:45 PM, Grze? wrote:

I have database write as .csv file.

The external sorage format is not likely to be relevant. What might  
be
informative would be to produce the code that reads this file.

When I want to get sth from my database I get NULL, but I know that
there is
sth!
For example:

data$ID

NULL

data$kod

NULL

So the names of your columns are not "ID" and "kod" but rather "X.ID."  
and "X.kod."

Try instead:
  data$X.ID.
#and:
  data$X.kkod.     # you will need to use both the periods if your  
column names end in periods.

but command like below is always recognize by R

data[2,3]

[1] '082'

That must have been a different version of data, since data[2,3] from  
the dataframe above should have been   the number 7  number rather  
than a string. I would also suggest that you start naming your  
data.frames something other than "data", since that is a reserved word  
used by quite a few functions.

Tell is what happens when you enter:

str(data)
class(data)

Perhaps the third column is not named "ID" or "kod" or the object is
not a data.frame, but is rather a matrix.

-- 
David Winsemius

In my opinion this problem is also connect with my attempt to create
a tree.
I always get errors.

t.tree0=rpart(ID~.,t.train)

Error in eval(expr, envir, enclos) : object "ID" not found

t.tree0=rpart(kod~.,t.train)

Error in eval(expr, envir, enclos) : object "kod" not found

What I should do to create my simple trees?

-- 

David Winsemius, MD
Heritage Laboratories
West Hartford, CT