Mixing
Usage of `…` (three-dots or dot-dot-dot) in functions
Where can I find documentation on the usage of ... in functions? Examples would be useful.
r ellipsis
edited Aug 29 '12 at 10:19
flodel
70.4k13138179
asked May 4 '11 at 22:26
Brandon BertelsenBrandon Bertelsen
25.4k27123228
add a comment |
Where can I find documentation on the usage of ... in functions? Examples would be useful.
r ellipsis
edited Aug 29 '12 at 10:19
flodel
70.4k13138179
asked May 4 '11 at 22:26
Brandon BertelsenBrandon Bertelsen
25.4k27123228
Do you mean database in functions? If so, I'd look the database vendor's documentation.
– octopusgrabbus
May 4 '11 at 22:29
2
For python users learning R, a quick answer would be that...is the R equivalent of python's keyword input (def func(**kwargs))
– Anna
May 9 '18 at 20:25
add a comment |
Where can I find documentation on the usage of ... in functions? Examples would be useful.
r ellipsis
edited Aug 29 '12 at 10:19
flodel
70.4k13138179
asked May 4 '11 at 22:26
Brandon BertelsenBrandon Bertelsen
25.4k27123228
Where can I find documentation on the usage of ... in functions? Examples would be useful.
r ellipsis
r ellipsis
edited Aug 29 '12 at 10:19
flodel
70.4k13138179
asked May 4 '11 at 22:26
Brandon BertelsenBrandon Bertelsen
25.4k27123228
edited Aug 29 '12 at 10:19
flodel
70.4k13138179
asked May 4 '11 at 22:26
Brandon BertelsenBrandon Bertelsen
25.4k27123228
edited Aug 29 '12 at 10:19
flodel
70.4k13138179
edited Aug 29 '12 at 10:19
flodel
70.4k13138179
edited Aug 29 '12 at 10:19
flodel
70.4k13138179
70.4k13138179
asked May 4 '11 at 22:26
Brandon BertelsenBrandon Bertelsen
25.4k27123228
asked May 4 '11 at 22:26
Brandon BertelsenBrandon Bertelsen
25.4k27123228
asked May 4 '11 at 22:26
Brandon BertelsenBrandon Bertelsen
25.4k27123228
25.4k27123228
Do you mean database in functions? If so, I'd look the database vendor's documentation.
– octopusgrabbus
May 4 '11 at 22:29
2
For python users learning R, a quick answer would be that...is the R equivalent of python's keyword input (def func(**kwargs))
– Anna
May 9 '18 at 20:25
add a comment |
Do you mean database in functions? If so, I'd look the database vendor's documentation.
– octopusgrabbus
May 4 '11 at 22:29
2
For python users learning R, a quick answer would be that...is the R equivalent of python's keyword input (def func(**kwargs))
– Anna
May 9 '18 at 20:25
Do you mean database in functions? If so, I'd look the database vendor's documentation.
– octopusgrabbus
May 4 '11 at 22:29
Do you mean database in functions? If so, I'd look the database vendor's documentation.
– octopusgrabbus
May 4 '11 at 22:29
2
2
For python users learning R, a quick answer would be that
... is the R equivalent of python's keyword input (def func(**kwargs))– Anna
May 9 '18 at 20:25
For python users learning R, a quick answer would be that
... is the R equivalent of python's keyword input (def func(**kwargs))– Anna
May 9 '18 at 20:25
add a comment |
3 Answers
3
active
oldest
votes
The word used to describe ... is "ellipsis." Knowing this should make searching for information about the construct easier. For example, the first hit on Google is another question on this site: How to use R's ellipsis feature when writing your own function?
edited May 23 '17 at 12:10
Community♦
11
answered May 4 '11 at 22:33
John ZwinckJohn Zwinck
152k16176292
add a comment |
A little example to get you started.
f <- function(x, ...)
{
dots <- list(...) #1
if(length(dots) == 0) return(NULL)
cat("The arguments in ... aren")
print(dots)
f(...) #2
}
f(1,2,3,"a", list("monkey"))
The function, f, stores all but the first input argument in the ellipsis variable. For accessing its contents, it is easiest to convert it to a list (1). The main use however is for passing arguments to subfunctions, which requires no conversion (2).
answered May 5 '11 at 10:53
Richie CottonRichie Cotton
79.9k27188307
Why in #2 call the same f function again?
– Jiapeng Zhang
Sep 9 '18 at 15:20
1
@JiapengZhang It's an example of a recursive function.f()gets called repeatedly with different arguments each time. Run the code and see if you can understand what is happening.
– Richie Cotton
Sep 10 '18 at 16:02
add a comment |
You should head over to "R Language Definition", section 2.1.9 Dot-dot-dot. It comes bundled with R installation. Run help.start() in an interactive session to bring HTML help up, and click on The R Language Definition link. You can use PDF or HTML version from the main site as well.
Anyway, ... is used to match unspecified formal arguments of a function.
args(sapply)
function (X, FUN, ..., simplify = TRUE, USE.NAMES = TRUE)
NULL
sapply(mtcars, mean, trim = .5)
mpg cyl disp hp drat wt qsec vs am gear
19.200 6.000 196.300 123.000 3.695 3.325 17.710 0.000 0.000 4.000
carb
2.000
As you can see, I passed trim = .5 though it's not specified as a formal argument of sapply function.
(note that this example is trivial, you can use sapply(mtcars, median) to achieve the same result)
answered May 5 '11 at 0:04
aL3xaaL3xa
23.2k1467101
1
If it's not specified, how do you know it's legal or valid?
– qed
Aug 3 '13 at 20:10
@qedtrimis an argument to themeanfunction. The...insapplyare the mechanism fortrimto be passed tomean.
– Richie Cotton
Mar 16 '15 at 10:34
add a comment |
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
The word used to describe ... is "ellipsis." Knowing this should make searching for information about the construct easier. For example, the first hit on Google is another question on this site: How to use R's ellipsis feature when writing your own function?
edited May 23 '17 at 12:10
Community♦
11
answered May 4 '11 at 22:33
John ZwinckJohn Zwinck
152k16176292
add a comment |
The word used to describe ... is "ellipsis." Knowing this should make searching for information about the construct easier. For example, the first hit on Google is another question on this site: How to use R's ellipsis feature when writing your own function?
edited May 23 '17 at 12:10
Community♦
11
answered May 4 '11 at 22:33
John ZwinckJohn Zwinck
152k16176292
add a comment |
The word used to describe ... is "ellipsis." Knowing this should make searching for information about the construct easier. For example, the first hit on Google is another question on this site: How to use R's ellipsis feature when writing your own function?
edited May 23 '17 at 12:10
Community♦
11
answered May 4 '11 at 22:33
John ZwinckJohn Zwinck
152k16176292
The word used to describe ... is "ellipsis." Knowing this should make searching for information about the construct easier. For example, the first hit on Google is another question on this site: How to use R's ellipsis feature when writing your own function?
edited May 23 '17 at 12:10
Community♦
11
answered May 4 '11 at 22:33
John ZwinckJohn Zwinck
152k16176292
edited May 23 '17 at 12:10
Community♦
11
edited May 23 '17 at 12:10
Community♦
11
edited May 23 '17 at 12:10
Community♦
11
11
answered May 4 '11 at 22:33
John ZwinckJohn Zwinck
152k16176292
answered May 4 '11 at 22:33
John ZwinckJohn Zwinck
152k16176292
answered May 4 '11 at 22:33
John ZwinckJohn Zwinck
152k16176292
152k16176292
add a comment |
add a comment |
A little example to get you started.
f <- function(x, ...)
{
dots <- list(...) #1
if(length(dots) == 0) return(NULL)
cat("The arguments in ... aren")
print(dots)
f(...) #2
}
f(1,2,3,"a", list("monkey"))
The function, f, stores all but the first input argument in the ellipsis variable. For accessing its contents, it is easiest to convert it to a list (1). The main use however is for passing arguments to subfunctions, which requires no conversion (2).
answered May 5 '11 at 10:53
Richie CottonRichie Cotton
79.9k27188307
Why in #2 call the same f function again?
– Jiapeng Zhang
Sep 9 '18 at 15:20
1
@JiapengZhang It's an example of a recursive function.f()gets called repeatedly with different arguments each time. Run the code and see if you can understand what is happening.
– Richie Cotton
Sep 10 '18 at 16:02
add a comment |
A little example to get you started.
f <- function(x, ...)
{
dots <- list(...) #1
if(length(dots) == 0) return(NULL)
cat("The arguments in ... aren")
print(dots)
f(...) #2
}
f(1,2,3,"a", list("monkey"))
The function, f, stores all but the first input argument in the ellipsis variable. For accessing its contents, it is easiest to convert it to a list (1). The main use however is for passing arguments to subfunctions, which requires no conversion (2).
answered May 5 '11 at 10:53
Richie CottonRichie Cotton
79.9k27188307
Why in #2 call the same f function again?
– Jiapeng Zhang
Sep 9 '18 at 15:20
1
@JiapengZhang It's an example of a recursive function.f()gets called repeatedly with different arguments each time. Run the code and see if you can understand what is happening.
– Richie Cotton
Sep 10 '18 at 16:02
add a comment |
A little example to get you started.
f <- function(x, ...)
{
dots <- list(...) #1
if(length(dots) == 0) return(NULL)
cat("The arguments in ... aren")
print(dots)
f(...) #2
}
f(1,2,3,"a", list("monkey"))
The function, f, stores all but the first input argument in the ellipsis variable. For accessing its contents, it is easiest to convert it to a list (1). The main use however is for passing arguments to subfunctions, which requires no conversion (2).
answered May 5 '11 at 10:53
Richie CottonRichie Cotton
79.9k27188307
A little example to get you started.
f <- function(x, ...)
{
dots <- list(...) #1
if(length(dots) == 0) return(NULL)
cat("The arguments in ... aren")
print(dots)
f(...) #2
}
f(1,2,3,"a", list("monkey"))
The function, f, stores all but the first input argument in the ellipsis variable. For accessing its contents, it is easiest to convert it to a list (1). The main use however is for passing arguments to subfunctions, which requires no conversion (2).
answered May 5 '11 at 10:53
Richie CottonRichie Cotton
79.9k27188307
answered May 5 '11 at 10:53
Richie CottonRichie Cotton
79.9k27188307
answered May 5 '11 at 10:53
Richie CottonRichie Cotton
79.9k27188307
answered May 5 '11 at 10:53
Richie CottonRichie Cotton
79.9k27188307
79.9k27188307
Why in #2 call the same f function again?
– Jiapeng Zhang
Sep 9 '18 at 15:20
1
@JiapengZhang It's an example of a recursive function.f()gets called repeatedly with different arguments each time. Run the code and see if you can understand what is happening.
– Richie Cotton
Sep 10 '18 at 16:02
add a comment |
Why in #2 call the same f function again?
– Jiapeng Zhang
Sep 9 '18 at 15:20
1
@JiapengZhang It's an example of a recursive function.f()gets called repeatedly with different arguments each time. Run the code and see if you can understand what is happening.
– Richie Cotton
Sep 10 '18 at 16:02
Why in #2 call the same f function again?
– Jiapeng Zhang
Sep 9 '18 at 15:20
Why in #2 call the same f function again?
– Jiapeng Zhang
Sep 9 '18 at 15:20
1
1
@JiapengZhang It's an example of a recursive function.
f() gets called repeatedly with different arguments each time. Run the code and see if you can understand what is happening.– Richie Cotton
Sep 10 '18 at 16:02
@JiapengZhang It's an example of a recursive function.
f() gets called repeatedly with different arguments each time. Run the code and see if you can understand what is happening.– Richie Cotton
Sep 10 '18 at 16:02
add a comment |
You should head over to "R Language Definition", section 2.1.9 Dot-dot-dot. It comes bundled with R installation. Run help.start() in an interactive session to bring HTML help up, and click on The R Language Definition link. You can use PDF or HTML version from the main site as well.
Anyway, ... is used to match unspecified formal arguments of a function.
args(sapply)
function (X, FUN, ..., simplify = TRUE, USE.NAMES = TRUE)
NULL
sapply(mtcars, mean, trim = .5)
mpg cyl disp hp drat wt qsec vs am gear
19.200 6.000 196.300 123.000 3.695 3.325 17.710 0.000 0.000 4.000
carb
2.000
As you can see, I passed trim = .5 though it's not specified as a formal argument of sapply function.
(note that this example is trivial, you can use sapply(mtcars, median) to achieve the same result)
answered May 5 '11 at 0:04
aL3xaaL3xa
23.2k1467101
1
If it's not specified, how do you know it's legal or valid?
– qed
Aug 3 '13 at 20:10
@qedtrimis an argument to themeanfunction. The...insapplyare the mechanism fortrimto be passed tomean.
– Richie Cotton
Mar 16 '15 at 10:34
add a comment |
You should head over to "R Language Definition", section 2.1.9 Dot-dot-dot. It comes bundled with R installation. Run help.start() in an interactive session to bring HTML help up, and click on The R Language Definition link. You can use PDF or HTML version from the main site as well.
Anyway, ... is used to match unspecified formal arguments of a function.
args(sapply)
function (X, FUN, ..., simplify = TRUE, USE.NAMES = TRUE)
NULL
sapply(mtcars, mean, trim = .5)
mpg cyl disp hp drat wt qsec vs am gear
19.200 6.000 196.300 123.000 3.695 3.325 17.710 0.000 0.000 4.000
carb
2.000
As you can see, I passed trim = .5 though it's not specified as a formal argument of sapply function.
(note that this example is trivial, you can use sapply(mtcars, median) to achieve the same result)
answered May 5 '11 at 0:04
aL3xaaL3xa
23.2k1467101
1
If it's not specified, how do you know it's legal or valid?
– qed
Aug 3 '13 at 20:10
@qedtrimis an argument to themeanfunction. The...insapplyare the mechanism fortrimto be passed tomean.
– Richie Cotton
Mar 16 '15 at 10:34
add a comment |
You should head over to "R Language Definition", section 2.1.9 Dot-dot-dot. It comes bundled with R installation. Run help.start() in an interactive session to bring HTML help up, and click on The R Language Definition link. You can use PDF or HTML version from the main site as well.
Anyway, ... is used to match unspecified formal arguments of a function.
args(sapply)
function (X, FUN, ..., simplify = TRUE, USE.NAMES = TRUE)
NULL
sapply(mtcars, mean, trim = .5)
mpg cyl disp hp drat wt qsec vs am gear
19.200 6.000 196.300 123.000 3.695 3.325 17.710 0.000 0.000 4.000
carb
2.000
As you can see, I passed trim = .5 though it's not specified as a formal argument of sapply function.
(note that this example is trivial, you can use sapply(mtcars, median) to achieve the same result)
answered May 5 '11 at 0:04
aL3xaaL3xa
23.2k1467101
You should head over to "R Language Definition", section 2.1.9 Dot-dot-dot. It comes bundled with R installation. Run help.start() in an interactive session to bring HTML help up, and click on The R Language Definition link. You can use PDF or HTML version from the main site as well.
Anyway, ... is used to match unspecified formal arguments of a function.
args(sapply)
function (X, FUN, ..., simplify = TRUE, USE.NAMES = TRUE)
NULL
sapply(mtcars, mean, trim = .5)
mpg cyl disp hp drat wt qsec vs am gear
19.200 6.000 196.300 123.000 3.695 3.325 17.710 0.000 0.000 4.000
carb
2.000
As you can see, I passed trim = .5 though it's not specified as a formal argument of sapply function.
(note that this example is trivial, you can use sapply(mtcars, median) to achieve the same result)
answered May 5 '11 at 0:04
aL3xaaL3xa
23.2k1467101
answered May 5 '11 at 0:04
aL3xaaL3xa
23.2k1467101
answered May 5 '11 at 0:04
aL3xaaL3xa
23.2k1467101
answered May 5 '11 at 0:04
aL3xaaL3xa
23.2k1467101
23.2k1467101
1
If it's not specified, how do you know it's legal or valid?
– qed
Aug 3 '13 at 20:10
@qedtrimis an argument to themeanfunction. The...insapplyare the mechanism fortrimto be passed tomean.
– Richie Cotton
Mar 16 '15 at 10:34
add a comment |
1
If it's not specified, how do you know it's legal or valid?
– qed
Aug 3 '13 at 20:10
@qedtrimis an argument to themeanfunction. The...insapplyare the mechanism fortrimto be passed tomean.
– Richie Cotton
Mar 16 '15 at 10:34
1
1
If it's not specified, how do you know it's legal or valid?
– qed
Aug 3 '13 at 20:10
If it's not specified, how do you know it's legal or valid?
– qed
Aug 3 '13 at 20:10
@qed
trim is an argument to the mean function. The ... in sapply are the mechanism for trim to be passed to mean.– Richie Cotton
Mar 16 '15 at 10:34
@qed
trim is an argument to the mean function. The ... in sapply are the mechanism for trim to be passed to mean.– Richie Cotton
Mar 16 '15 at 10:34
add a comment |
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Do you mean database in functions? If so, I'd look the database vendor's documentation.
– octopusgrabbus
May 4 '11 at 22:29
2
For python users learning R, a quick answer would be that
...is the R equivalent of python's keyword input (def func(**kwargs))– Anna
May 9 '18 at 20:25