R help - Jul 2010 - specifying column names in a vector of characters and the use?

Hi,

What I would like to do is have a data.frame with column names and have
these column names stored as strings in another vector.  Then I would like
to be able to access the data.fram columns via referencing the vector of
names.  The code below shows the last few executions that failed to retrieve
the values for column named X1.  Seth

> table.1<-cbind(c(1,2,3,2,2),c(0,9,0,7,9),c(7,5,9,8,8))
> table.1
     [,1] [,2] [,3]
[1,]    1    0    7
[2,]    2    9    5
[3,]    3    0    9
[4,]    2    7    8
[5,]    2    9    8
> 
> table.1<-data.frame(table.1)
> table.1
  X1 X2 X3
1  1  0  7
2  2  9  5
3  3  0  9
4  2  7  8
5  2  9  8
> hold<-c("X1","X2","X3")
> hold
[1] "X1" "X2" "X3"
> table.1$X1
[1] 1 2 3 2 2
> hold[1]
[1] "X1"
> table.1$hold[1] # FROM HERE DOWN ARE MY ATTEMPTS TO ACCESS X1
NULL
> table.1$(hold[1])
Error: unexpected '(' in "table.1$("
> table.1$get(hold[1])
Error: attempt to apply non-function
> table.1$(get(hold[1]))
Error: unexpected '(' in "table.1$("
> 
-- 
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Sent from the R help mailing list archive at Nabble.com.

Try:

table.1[[hold[1]]]

Cheers,

Simon.


On 19/07/10 12:09, Seth wrote:
> Hi,
>
> What I would like to do is have a data.frame with column names and have
> these column names stored as strings in another vector.  Then I would like
> to be able to access the data.fram columns via referencing the vector of
> names.  The code below shows the last few executions that failed to
retrieve
> the values for column named X1.  Seth
>
>
>    
>> table.1<-cbind(c(1,2,3,2,2),c(0,9,0,7,9),c(7,5,9,8,8))
>> table.1
>>      
>       [,1] [,2] [,3]
> [1,]    1    0    7
> [2,]    2    9    5
> [3,]    3    0    9
> [4,]    2    7    8
> [5,]    2    9    8
>    
>> table.1<-data.frame(table.1)
>> table.1
>>      
>    X1 X2 X3
> 1  1  0  7
> 2  2  9  5
> 3  3  0  9
> 4  2  7  8
> 5  2  9  8
>    
>> hold<-c("X1","X2","X3")
>> hold
>>      
> [1] "X1" "X2" "X3"
>    
>> table.1$X1
>>      
> [1] 1 2 3 2 2
>    
>> hold[1]
>>      
> [1] "X1"
>    
>> table.1$hold[1] # FROM HERE DOWN ARE MY ATTEMPTS TO ACCESS X1
>>      
> NULL
>    
>> table.1$(hold[1])
>>      
> Error: unexpected '(' in "table.1$("
>    
>> table.1$get(hold[1])
>>      
> Error: attempt to apply non-function
>    
>> table.1$(get(hold[1]))
>>      
> Error: unexpected '(' in "table.1$("
>    
>>      
-- 
Simon Blomberg, BSc (Hons), PhD, MAppStat.
Lecturer and Consultant Statistician
School of Biological Sciences
The University of Queensland
St. Lucia Queensland 4072
Australia
T: +61 7 3365 2506
email: S.Blomberg1_at_uq.edu.au
http://www.uq.edu.au/~uqsblomb/

Policies:
1.  I will NOT analyse your data for you.
2.  Your deadline is your problem

Statistics is the grammar of science - Karl Pearson.

Hello,
> What I would like to do is have a data.frame with column names and have
> these column names stored as strings in another vector.  Then I would like
> to be able to access the data.fram columns via referencing the vector of
> names.  The code below shows the last few executions that failed to
retrieve
> the values for column named X1.  Seth
>
>
>> table.1<-cbind(c(1,2,3,2,2),c(0,9,0,7,9),c(7,5,9,8,8))
>> table.1
>       [,1] [,2] [,3]
> [1,]    1    0    7
> [2,]    2    9    5
> [3,]    3    0    9
> [4,]    2    7    8
> [5,]    2    9    8
See easier way to construct your object below.

<snip>
> [1] "X1"
>> table.1$hold[1] # FROM HERE DOWN ARE MY ATTEMPTS TO ACCESS X1
> NULL
>> table.1$(hold[1])
> Error: unexpected '(' in "table.1$("
>> table.1$get(hold[1])
> Error: attempt to apply non-function
>> table.1$(get(hold[1]))
> Error: unexpected '(' in "table.1$("
You need to index with ?[

Here is a complete example:

table.1<- data.frame(X1 = c(1,2,3,2,2),
                      X2 = c(0,9,0,7,9),
                      X3 = c(7,5,9,8,8))

hold <- names(table.1)

## to return a data.frame
table.1[hold[1]]

## to return a vector
table.1[[hold[1]]]

On Jul 18, 2010, at 10:09 PM, Seth wrote:
>
> Hi,
>
> What I would like to do is have a data.frame with column names and  
> have
> these column names stored as strings in another vector.  Then I  
> would like
> to be able to access the data.fram columns via referencing the  
> vector of
> names.  The code below shows the last few executions that failed to  
> retrieve
> the values for column named X1.  Seth
>
>
>> table.1<-cbind(c(1,2,3,2,2),c(0,9,0,7,9),c(7,5,9,8,8))
>> table.1
>     [,1] [,2] [,3]
> [1,]    1    0    7
> [2,]    2    9    5
> [3,]    3    0    9
> [4,]    2    7    8
> [5,]    2    9    8
>>
>> table.1<-data.frame(table.1)
>> table.1
>  X1 X2 X3
> 1  1  0  7
> 2  2  9  5
> 3  3  0  9
> 4  2  7  8
> 5  2  9  8
>> hold<-c("X1","X2","X3")
>> hold
> [1] "X1" "X2" "X3"
>> table.1$X1
> [1] 1 2 3 2 2
>> hold[1]
> [1] "X1"
>> table.1$hold[1] # FROM HERE DOWN ARE MY ATTEMPTS TO ACCESS X1
> NULL
Try instead:

table.1[ , hold[1] ]

The "$" formalism does not evaluate its argument, but the
"[" function
does.

-- 
David.
>> table.1$(hold[1])
> Error: unexpected '(' in "table.1$("
>> table.1$get(hold[1])
> Error: attempt to apply non-function
>> table.1$(get(hold[1]))
> Error: unexpected '(' in "table.1$("
>>
> -- 
> View this message in context:
http://r.789695.n4.nabble.com/specifying-column-names-in-a-vector-of-characters-and-the-use-tp2293494p2293494.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
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