Re: [R] Function with 'data' parameter
Thanks, worked like a charm.
Greg.
On Feb 22, 1:58 pm, Gavin Simpson gavin.simp...@ucl.ac.uk wrote:
On Sun, 2009-02-22 at 20:52 +1100, Jim Lemon wrote:
Greg wrote:
I'm trying to write a simple function with a data parameter.
tfun - function(x, y, data = NULL) {
if(missing(data))
dt - data.frame(x=x, group=y)
else {
dt - with(data, data.frame(x=x, group=y))
}
return(dt)
}
If I pass variables weight and grp from a data.frame, d, like
this: tfun(d$weight, d$grp), the function works. However, if I try to
do the same thing by supplying d, like this: tfun(weight, grp,
data=d), I receive the following error:
Error in data.frame(x = x, group = y) : object weight not found
Can someone please tell me what I'm doing wrong?
Hi Greg,
In your function definition, the data argument isn't missing, it's NULL.
You have to test like this:
if(is.null(data)) ...
Does that fix it?
No, because x and y are still being evaluated and are not present
anywhere but within 'd'. (I converted the function definition to
function(x, y, data) and checked that it was executing the else clause
when data was *not* missing.)
You could do:
## dummy data
set.seed(1234)
d - data.frame(weight = rnorm(10),
grp = rnorm(10))
tfun2 - function(x, y, data) {
x - deparse(substitute(x))
y - deparse(substitute(y))
if(missing(data))
dt - data.frame(x=x, group=y)
else {
dt - with(data, data.frame(x=data[[x]], group=data[[y]]))
}
return(dt)
}
tfun2(weight, grp, data = d)
but that seems a little ugly. Alternatively, make use of a model formula
and in-built functionality
tfun3 - function(formula, data) {
dat - model.frame(formula, data)
names(dat) - c(x, group)
return(dat)
}
tfun3(weight ~ grp, data = d)
HTH
G
--
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Dr. Gavin Simpson [t] +44 (0)20 7679 0522
ECRC, UCL Geography, [f] +44 (0)20 7679 0565
Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk
Gower Street, London [w]http://www.ucl.ac.uk/~ucfagls/
UK. WC1E 6BT. [w]http://www.freshwaters.org.uk
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Re: [R] Function with 'data' parameter
Greg wrote:
I'm trying to write a simple function with a data parameter.
tfun - function(x, y, data = NULL) {
if(missing(data))
dt - data.frame(x=x, group=y)
else {
dt - with(data, data.frame(x=x, group=y))
}
return(dt)
}
If I pass variables weight and grp from a data.frame, d, like
this: tfun(d$weight, d$grp), the function works. However, if I try to
do the same thing by supplying d, like this: tfun(weight, grp,
data=d), I receive the following error:
Error in data.frame(x = x, group = y) : object weight not found
Can someone please tell me what I'm doing wrong?
Hi Greg,
In your function definition, the data argument isn't missing, it's NULL.
You have to test like this:
if(is.null(data)) ...
Does that fix it?
Jim
__
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
Re: [R] Function with 'data' parameter
On Sun, 2009-02-22 at 20:52 +1100, Jim Lemon wrote:
Greg wrote:
I'm trying to write a simple function with a data parameter.
tfun - function(x, y, data = NULL) {
if(missing(data))
dt - data.frame(x=x, group=y)
else {
dt - with(data, data.frame(x=x, group=y))
}
return(dt)
}
If I pass variables weight and grp from a data.frame, d, like
this: tfun(d$weight, d$grp), the function works. However, if I try to
do the same thing by supplying d, like this: tfun(weight, grp,
data=d), I receive the following error:
Error in data.frame(x = x, group = y) : object weight not found
Can someone please tell me what I'm doing wrong?
Hi Greg,
In your function definition, the data argument isn't missing, it's NULL.
You have to test like this:
if(is.null(data)) ...
Does that fix it?
No, because x and y are still being evaluated and are not present
anywhere but within 'd'. (I converted the function definition to
function(x, y, data) and checked that it was executing the else clause
when data was *not* missing.)
You could do:
## dummy data
set.seed(1234)
d - data.frame(weight = rnorm(10),
grp = rnorm(10))
tfun2 - function(x, y, data) {
x - deparse(substitute(x))
y - deparse(substitute(y))
if(missing(data))
dt - data.frame(x=x, group=y)
else {
dt - with(data, data.frame(x=data[[x]], group=data[[y]]))
}
return(dt)
}
tfun2(weight, grp, data = d)
but that seems a little ugly. Alternatively, make use of a model formula
and in-built functionality
tfun3 - function(formula, data) {
dat - model.frame(formula, data)
names(dat) - c(x, group)
return(dat)
}
tfun3(weight ~ grp, data = d)
HTH
G
--
%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
Dr. Gavin Simpson [t] +44 (0)20 7679 0522
ECRC, UCL Geography, [f] +44 (0)20 7679 0565
Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk
Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/
UK. WC1E 6BT. [w] http://www.freshwaters.org.uk
%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%
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