Re: [R] How to make attributes persist after indexing?
Thank you Mark, for this helpful explanation. I noted the class labelled
in Hmisc, but did not yet study it well.
My example was just to see if attributes persist, but my main motivation is
to use value labels for numerical variables and factors to solve my
problem of how to represent a metric categorical variable.
From an other discussion (attributes of a data.frame, Tue 22 Nov 2005) I
understood that there is very little interest in labelling variables, and I
assume even less in labelling variable values.
In my work, however categorical variables with an inherent metric (e.g.
risk scores) occur frequently and I think they could best be treated as
numeric with attached value.labels so that they can be converted easily to
factors if needed for use in a function.
So I have to see how convenient it is to introduce a labelled.labelled
class.
Thanks,
Heinz
At 21:37 24.05.2006 -0500, Marc Schwartz wrote:
On Thu, 2006-05-25 at 00:43 +0100, Heinz Tuechler wrote:
Thank you for your answer, Gabor. I will see, if I understood it.
Heinz
At 11:31 24.05.2006 -0400, Gabor Grothendieck wrote:
You could create your own child class with its own [ method.
[.myfactor - function(x, ...) {
attr - attributes(x)
x - NextMethod([)
attributes(x) - attr
x
}
gx - structure(fx, class = c(myfactor, class(fx)))
attributes(gx[1])
Heinz,
What Gabor has proposed is essentially what Frank Harrell does in the
Hmisc package (which I referenced), though in a more generic fashion
with respect to the attributes that are saved and reset.
By using:
gx - structure(fx, class = c(myfactor, class(fx)))
you are taking an object 'fx' and adding a child class attribute called
myfactor to it. So it is in effect an object that retains the
attributes of the original class of 'fx', plus the new class attribute
'myfactor'.
As a parallel, for example, consider that a square is a child class of a
rectangle. A square inherits all of the attributes of a rectangle, plus
the additional attribute that all four sides are of equal length. So for
example, if 'x' is a square, you might see:
x
[1] 4 4 4 4
attr(,class)
[1] squarerectangle
as compared to a rectangle 'y':
y
[1] 4 2 4 2
attr(,class)
[1] rectangle
Note the two class attributes for 'x', with 'square' preceding
'rectangle' in the order. The order is important, because in R, function
methods are dispatched based upon the class attributes in the order that
they appear in the vector.
So...back to 'gx'.
When the generic [ function is called with gx (ie. gx[1]), the first
class attribute 'myfactor' is picked up from 'gx'. Then, the method that
Gabor has presented, [.myfactor, is dispatched (executed). It is the
generic function [ with the specific class method defined by
.myfactor.
In that function, the first thing that takes place is that the
attributes of the 'x' argument are saved in 'attr'.
attr - attributes(x)
This would include any new attributes that you have defined and added,
such as labels and comments.
The next thing that happens is that the generic [ is now called again:
x - NextMethod([)
but this time, the method dispatched is based upon the Next entry in
the class vector. In this case, whatever the original class of 'fx' was,
which could be an atomic vector, a factor, a matrix or a data frame, for
example.
You can see the methods available for [ by using:
methods([)
The appropriate method for [ is then executed, resulting in 'x', which
is the subset version of 'gx'.
Then:
attributes(x) - attr
restores the original attributes saved in 'attr' to 'x'.
Then, finally, the 'x' object is returned to the calling environment.
So, in effect, you have created a new subset function [ that retains
your new attributes. The great thing about this, is that once the method
is defined in your working environment, all you have to do is to add the
newly associated class attribute to the objects you want to subset and R
does the rest transparently.
Thus:
# Add the new method
[.myfactor - function(x, ...) {
attr - attributes(x)
x - NextMethod([)
attributes(x) - attr
x
}
# Create fx
fx - factor(1:5, ordered = TRUE)
attr(fx, 'comment') - 'Comment for fx'
attr(fx, 'label') - 'Label for fx'
attr(fx, 'testattribute') - 'just for fun'
attributes(fx)
$levels
[1] 1 2 3 4 5
$class
[1] ordered factor
$comment
[1] Comment for fx
$label
[1] Label for fx
$testattribute
[1] just for fun
# Create gx, which is identical to fx, with the
# additional class attribute
gx - structure(fx, class = c(myfactor, class(fx)))
attributes(gx)
$levels
[1] 1 2 3 4 5
$class
[1] myfactor ordered factor # - Note change here
$comment
[1] Comment for fx
$label
[1] Label for fx
$testattribute
[1] just for fun
# Show the structure of fx[1]
# Note that other attributes are lost
str(fx[1])
Ord.factor w/ 5 levels 1234..: 1
# Show the structure of gx[1]
# Note that attributes are retained
str(gx[1])
[R] How to make attributes persist after indexing?
Dear All! For descriptive purposes I would like to add attributes to objects. These attributes should be kept, even if by indexing only part of the object is used. I noted that some attributes like levels and class of a factor exist also after indexing, while others, like comment or label vanish. Is there a way to make an arbitrary attribute to be kept after indexing? This would be especially useful when indexing a data.frame. ## example for loss of attributes fx - factor(1:5, ordered=TRUE) attr(fx, 'comment') - 'Comment for fx' attr(fx, 'label') - 'Label for fx' attr(fx, 'testattribute') - 'just for fun' attributes(fx) # all attributes are shown attributes(fx[])# all attributes are shown attributes(fx[1:5]) # only levels and class are shown attributes(fx[1]) # only levels and class are shown Thanks, Heinz Tüchler __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] How to make attributes persist after indexing?
You could create your own child class with its own [ method.
[.myfactor - function(x, ...) {
attr - attributes(x)
x - NextMethod([)
attributes(x) - attr
x
}
gx - structure(fx, class = c(myfactor, class(fx)))
attributes(gx[1])
On 5/24/06, Heinz Tuechler [EMAIL PROTECTED] wrote:
Dear All!
For descriptive purposes I would like to add attributes to objects. These
attributes should be kept, even if by indexing only part of the object is
used.
I noted that some attributes like levels and class of a factor exist also
after indexing, while others, like comment or label vanish.
Is there a way to make an arbitrary attribute to be kept after indexing?
This would be especially useful when indexing a data.frame.
## example for loss of attributes
fx - factor(1:5, ordered=TRUE)
attr(fx, 'comment') - 'Comment for fx'
attr(fx, 'label') - 'Label for fx'
attr(fx, 'testattribute') - 'just for fun'
attributes(fx) # all attributes are shown
attributes(fx[])# all attributes are shown
attributes(fx[1:5]) # only levels and class are shown
attributes(fx[1]) # only levels and class are shown
Thanks,
Heinz Tüchler
__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] How to make attributes persist after indexing?
On Wed, 2006-05-24 at 17:20 +0100, Heinz Tuechler wrote: Dear All! For descriptive purposes I would like to add attributes to objects. These attributes should be kept, even if by indexing only part of the object is used. I noted that some attributes like levels and class of a factor exist also after indexing, while others, like comment or label vanish. Is there a way to make an arbitrary attribute to be kept after indexing? This would be especially useful when indexing a data.frame. ## example for loss of attributes fx - factor(1:5, ordered=TRUE) attr(fx, 'comment') - 'Comment for fx' attr(fx, 'label') - 'Label for fx' attr(fx, 'testattribute') - 'just for fun' attributes(fx) # all attributes are shown attributes(fx[])# all attributes are shown attributes(fx[1:5]) # only levels and class are shown attributes(fx[1]) # only levels and class are shown Thanks, Heinz Tüchler Non-standard attributes do not survive the use of [. You could create a new class and subset method for the objects where you require this type of functionality. Frank Harrell has done that in the Hmisc package to support the use of the labeling attributes, which in turn are used by some of his functions such as latex(). You might want to review what he has done in ?label where the [.labelled method has been added. Alternatively, you could create your own function to save the attributes, do the subsetting and then restore the attributes to the resultant object. HTH, Marc Schwartz __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] How to make attributes persist after indexing?
Thank you for your answer, Gabor. I will see, if I understood it.
Heinz
At 11:31 24.05.2006 -0400, Gabor Grothendieck wrote:
You could create your own child class with its own [ method.
[.myfactor - function(x, ...) {
attr - attributes(x)
x - NextMethod([)
attributes(x) - attr
x
}
gx - structure(fx, class = c(myfactor, class(fx)))
attributes(gx[1])
On 5/24/06, Heinz Tuechler [EMAIL PROTECTED] wrote:
Dear All!
For descriptive purposes I would like to add attributes to objects. These
attributes should be kept, even if by indexing only part of the object is
used.
I noted that some attributes like levels and class of a factor exist also
after indexing, while others, like comment or label vanish.
Is there a way to make an arbitrary attribute to be kept after indexing?
This would be especially useful when indexing a data.frame.
## example for loss of attributes
fx - factor(1:5, ordered=TRUE)
attr(fx, 'comment') - 'Comment for fx'
attr(fx, 'label') - 'Label for fx'
attr(fx, 'testattribute') - 'just for fun'
attributes(fx) # all attributes are shown
attributes(fx[])# all attributes are shown
attributes(fx[1:5]) # only levels and class are shown
attributes(fx[1]) # only levels and class are shown
Thanks,
Heinz Tüchler
__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] How to make attributes persist after indexing?
On Thu, 2006-05-25 at 00:43 +0100, Heinz Tuechler wrote:
Thank you for your answer, Gabor. I will see, if I understood it.
Heinz
At 11:31 24.05.2006 -0400, Gabor Grothendieck wrote:
You could create your own child class with its own [ method.
[.myfactor - function(x, ...) {
attr - attributes(x)
x - NextMethod([)
attributes(x) - attr
x
}
gx - structure(fx, class = c(myfactor, class(fx)))
attributes(gx[1])
Heinz,
What Gabor has proposed is essentially what Frank Harrell does in the
Hmisc package (which I referenced), though in a more generic fashion
with respect to the attributes that are saved and reset.
By using:
gx - structure(fx, class = c(myfactor, class(fx)))
you are taking an object 'fx' and adding a child class attribute called
myfactor to it. So it is in effect an object that retains the
attributes of the original class of 'fx', plus the new class attribute
'myfactor'.
As a parallel, for example, consider that a square is a child class of a
rectangle. A square inherits all of the attributes of a rectangle, plus
the additional attribute that all four sides are of equal length. So for
example, if 'x' is a square, you might see:
x
[1] 4 4 4 4
attr(,class)
[1] squarerectangle
as compared to a rectangle 'y':
y
[1] 4 2 4 2
attr(,class)
[1] rectangle
Note the two class attributes for 'x', with 'square' preceding
'rectangle' in the order. The order is important, because in R, function
methods are dispatched based upon the class attributes in the order that
they appear in the vector.
So...back to 'gx'.
When the generic [ function is called with gx (ie. gx[1]), the first
class attribute 'myfactor' is picked up from 'gx'. Then, the method that
Gabor has presented, [.myfactor, is dispatched (executed). It is the
generic function [ with the specific class method defined by
.myfactor.
In that function, the first thing that takes place is that the
attributes of the 'x' argument are saved in 'attr'.
attr - attributes(x)
This would include any new attributes that you have defined and added,
such as labels and comments.
The next thing that happens is that the generic [ is now called again:
x - NextMethod([)
but this time, the method dispatched is based upon the Next entry in
the class vector. In this case, whatever the original class of 'fx' was,
which could be an atomic vector, a factor, a matrix or a data frame, for
example.
You can see the methods available for [ by using:
methods([)
The appropriate method for [ is then executed, resulting in 'x', which
is the subset version of 'gx'.
Then:
attributes(x) - attr
restores the original attributes saved in 'attr' to 'x'.
Then, finally, the 'x' object is returned to the calling environment.
So, in effect, you have created a new subset function [ that retains
your new attributes. The great thing about this, is that once the method
is defined in your working environment, all you have to do is to add the
newly associated class attribute to the objects you want to subset and R
does the rest transparently.
Thus:
# Add the new method
[.myfactor - function(x, ...) {
attr - attributes(x)
x - NextMethod([)
attributes(x) - attr
x
}
# Create fx
fx - factor(1:5, ordered = TRUE)
attr(fx, 'comment') - 'Comment for fx'
attr(fx, 'label') - 'Label for fx'
attr(fx, 'testattribute') - 'just for fun'
attributes(fx)
$levels
[1] 1 2 3 4 5
$class
[1] ordered factor
$comment
[1] Comment for fx
$label
[1] Label for fx
$testattribute
[1] just for fun
# Create gx, which is identical to fx, with the
# additional class attribute
gx - structure(fx, class = c(myfactor, class(fx)))
attributes(gx)
$levels
[1] 1 2 3 4 5
$class
[1] myfactor ordered factor # - Note change here
$comment
[1] Comment for fx
$label
[1] Label for fx
$testattribute
[1] just for fun
# Show the structure of fx[1]
# Note that other attributes are lost
str(fx[1])
Ord.factor w/ 5 levels 1234..: 1
# Show the structure of gx[1]
# Note that attributes are retained
str(gx[1])
Ord.factor w/ 5 levels 1234..: 1
- attr(*, comment)= chr Comment for fx
- attr(*, label)= chr Label for fx
- attr(*, testattribute)= chr just for fun
HTH,
Marc Schwartz
__
R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
