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David L Carlson

2016-Aug-24 15:54 UTC

[R] aggregate

Your is fine, but it will be a little simpler if you use sapply() instead:
> data.frame(Z=levels(myData$Z), CP=sapply(split(myData, myData$Z), +     function(x) crossprod(x[, 1], x[, 2])))
  Z CP
A A 10
B B 10

David C


-----Original Message-----
From: Gang Chen [mailto:gangchen6 at gmail.com] 
Sent: Wednesday, August 24, 2016 10:17 AM
To: David L Carlson
Cc: Jim Lemon; r-help mailing list
Subject: Re: [R] aggregate

Thank you all for the suggestions! Yes, I'm looking for the cross
product between the two columns of X and Y.

A follow-up question: what is a nice way to merge the output of

lapply(split(myData, myData$Z), function(x) crossprod(x[, 1], x[, 2]))

with the column Z in myData so that I would get a new dataframe as the
following (the 2nd column is the cross product between X and Y)?

Z   CP
A   10
B   10

Is the following legitimate?

data.frame(Z=levels(myData$Z), CP= unlist(lapply(split(myData,
myData$Z), function(x) crossprod(x[, 1], x[, 2]))))


On Wed, Aug 24, 2016 at 10:37 AM, David L Carlson <dcarlson at tamu.edu>
wrote:> Thank you for the reproducible example, but it is not clear what cross
product you want. Jim's solution gives you the cross product of the 2-column
matrix with itself. If you want the cross product between the columns you need
something else. The aggregate function will not work since it will treat the
columns separately:
>
>> A <- as.matrix(myData[myData$Z=="A", 1:2])
>> A
>   X Y
> 1 1 4
> 2 2 3
>> crossprod(A) # Same as t(A) %*% A
>    X  Y
> X  5 10
> Y 10 25
>> crossprod(A[, 1], A[, 2]) # Same as t(A[, 1] %*% A[, 2]
>      [,1]
> [1,]   10
>>
>> # For all the groups
>> lapply(split(myData, myData$Z), function(x) crossprod(as.matrix(x[,
1:2])))
> $A
>    X  Y
> X  5 10
> Y 10 25
>
> $B
>    X  Y
> X 25 10
> Y 10  5
>
>> lapply(split(myData, myData$Z), function(x) crossprod(x[, 1], x[, 2]))
> $A
>      [,1]
> [1,]   10
>
> $B
>      [,1]
> [1,]   10
>
> -------------------------------------
> David L Carlson
> Department of Anthropology
> Texas A&M University
> College Station, TX 77840-4352
>
>
> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Jim
Lemon
> Sent: Tuesday, August 23, 2016 6:02 PM
> To: Gang Chen; r-help mailing list
> Subject: Re: [R] aggregate
>
> Hi Gang Chen,
> If I have the right idea:
>
> for(zval in levels(myData$Z))
> crossprod(as.matrix(myData[myData$Z==zval,c("X","Y")]))
>
> Jim
>
> On Wed, Aug 24, 2016 at 8:03 AM, Gang Chen <gangchen6 at gmail.com>
wrote:
>> This is a simple question: With a dataframe like the following
>>
>> myData <- data.frame(X=c(1, 2, 3, 4), Y=c(4, 3, 2, 1),
Z=c('A', 'A', 'B', 'B'))
>>
>> how can I get the cross product between X and Y for each level of
>> factor Z? My difficulty is that I don't know how to deal with the
fact
>> that crossprod() acts on two variables in this case.
>>
>> ______________________________________________
>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> 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.
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.

Gang Chen

2016-Aug-24 16:55 UTC

head link

[R] aggregate

Thanks a lot, David! I want to further expand the operation a little
bit. With a new dataframe:

myData <- data.frame(X=c(1, 2, 3, 4, 5, 6, 7, 8), Y=c(8, 7, 6, 5, 4,
3, 2, 1), S=c(?S1?, ?S1?, ?S1?, ?S1?, ?S2?, ?S2?, ?S2?, ?S2?),
Z=c(?A?, ?A?, ?B?, ?B?, ?A?, ?A?, ?B?, ?B?))
> myData
  X Y  S Z
1 1 8 S1 A
2 2 7 S1 A
3 3 6 S1 B
4 4 5 S1 B
5 5 4 S2 A
6 6 3 S2 A
7 7 2 S2 B
8 8 1 S2 B

I would like to obtain the same cross product between columns X and Y,
but at each combination level of factors S and Z. In other words, the
cross product would be still performed each two rows in the new
dataframe myData. How can I achieve that?

On Wed, Aug 24, 2016 at 11:54 AM, David L Carlson <dcarlson at tamu.edu>
wrote:> Your is fine, but it will be a little simpler if you use sapply() instead:
>
>> data.frame(Z=levels(myData$Z), CP=sapply(split(myData, myData$Z),
> +     function(x) crossprod(x[, 1], x[, 2])))
>   Z CP
> A A 10
> B B 10
>
> David C
>
>
> -----Original Message-----
> From: Gang Chen [mailto:gangchen6 at gmail.com]
> Sent: Wednesday, August 24, 2016 10:17 AM
> To: David L Carlson
> Cc: Jim Lemon; r-help mailing list
> Subject: Re: [R] aggregate
>
> Thank you all for the suggestions! Yes, I'm looking for the cross
> product between the two columns of X and Y.
>
> A follow-up question: what is a nice way to merge the output of
>
> lapply(split(myData, myData$Z), function(x) crossprod(x[, 1], x[, 2]))
>
> with the column Z in myData so that I would get a new dataframe as the
> following (the 2nd column is the cross product between X and Y)?
>
> Z   CP
> A   10
> B   10
>
> Is the following legitimate?
>
> data.frame(Z=levels(myData$Z), CP= unlist(lapply(split(myData,
> myData$Z), function(x) crossprod(x[, 1], x[, 2]))))
>
>
> On Wed, Aug 24, 2016 at 10:37 AM, David L Carlson <dcarlson at
tamu.edu> wrote:
>> Thank you for the reproducible example, but it is not clear what cross
product you want. Jim's solution gives you the cross product of the 2-column
matrix with itself. If you want the cross product between the columns you need
something else. The aggregate function will not work since it will treat the
columns separately:
>>
>>> A <- as.matrix(myData[myData$Z=="A", 1:2])
>>> A
>>   X Y
>> 1 1 4
>> 2 2 3
>>> crossprod(A) # Same as t(A) %*% A
>>    X  Y
>> X  5 10
>> Y 10 25
>>> crossprod(A[, 1], A[, 2]) # Same as t(A[, 1] %*% A[, 2]
>>      [,1]
>> [1,]   10
>>>
>>> # For all the groups
>>> lapply(split(myData, myData$Z), function(x) crossprod(as.matrix(x[,
1:2])))
>> $A
>>    X  Y
>> X  5 10
>> Y 10 25
>>
>> $B
>>    X  Y
>> X 25 10
>> Y 10  5
>>
>>> lapply(split(myData, myData$Z), function(x) crossprod(x[, 1], x[,
2]))
>> $A
>>      [,1]
>> [1,]   10
>>
>> $B
>>      [,1]
>> [1,]   10
>>
>> -------------------------------------
>> David L Carlson
>> Department of Anthropology
>> Texas A&M University
>> College Station, TX 77840-4352
>>
>>
>> -----Original Message-----
>> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Jim
Lemon
>> Sent: Tuesday, August 23, 2016 6:02 PM
>> To: Gang Chen; r-help mailing list
>> Subject: Re: [R] aggregate
>>
>> Hi Gang Chen,
>> If I have the right idea:
>>
>> for(zval in levels(myData$Z))
>>
crossprod(as.matrix(myData[myData$Z==zval,c("X","Y")]))
>>
>> Jim
>>
>> On Wed, Aug 24, 2016 at 8:03 AM, Gang Chen <gangchen6 at
gmail.com> wrote:
>>> This is a simple question: With a dataframe like the following
>>>
>>> myData <- data.frame(X=c(1, 2, 3, 4), Y=c(4, 3, 2, 1),
Z=c('A', 'A', 'B', 'B'))
>>>
>>> how can I get the cross product between X and Y for each level of
>>> factor Z? My difficulty is that I don't know how to deal with
the fact
>>> that crossprod() acts on two variables in this case.
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more,
see
>>> 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.
>>
>> ______________________________________________
>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> 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.

David L Carlson

2016-Aug-24 17:07 UTC

head link

[R] aggregate

You need to spend some time with a basic R tutorial. Your data is messed up
because you did not use a simple text editor somewhere along the way. R
understands ', but not ? or ?. The best way to send data to the list is to
use dput:
> dput(myData)structure(list(X = c(1, 2, 3, 4, 5, 6, 7, 8), Y = c(8, 7, 6, 
5, 4, 3, 2, 1), S = structure(c(1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L
), .Label = c("S1", "S2"), class = "factor"), Z =
structure(c(1L,
1L, 2L, 2L, 1L, 1L, 2L, 2L), .Label = c("A", "B"), class =
"factor")), .Names = c("X",
"Y", "S", "Z"), row.names = c(NA, -8L), class =
"data.frame")

Combining two labels just requires the paste0() function:
> sapply(split(myData, paste0(myData$S, myData$Z)), function(x) crossprod(x[,
1], x[, 2]))S1A S1B S2A S2B 
 22  38  38  22

David C

-----Original Message-----
From: Gang Chen [mailto:gangchen6 at gmail.com] 
Sent: Wednesday, August 24, 2016 11:56 AM
To: David L Carlson
Cc: Jim Lemon; r-help mailing list
Subject: Re: [R] aggregate

Thanks a lot, David! I want to further expand the operation a little
bit. With a new dataframe:

myData <- data.frame(X=c(1, 2, 3, 4, 5, 6, 7, 8), Y=c(8, 7, 6, 5, 4,
3, 2, 1), S=c(?S1?, ?S1?, ?S1?, ?S1?, ?S2?, ?S2?, ?S2?, ?S2?),
Z=c(?A?, ?A?, ?B?, ?B?, ?A?, ?A?, ?B?, ?B?))
> myData
  X Y  S Z
1 1 8 S1 A
2 2 7 S1 A
3 3 6 S1 B
4 4 5 S1 B
5 5 4 S2 A
6 6 3 S2 A
7 7 2 S2 B
8 8 1 S2 B

I would like to obtain the same cross product between columns X and Y,
but at each combination level of factors S and Z. In other words, the
cross product would be still performed each two rows in the new
dataframe myData. How can I achieve that?

On Wed, Aug 24, 2016 at 11:54 AM, David L Carlson <dcarlson at tamu.edu>
wrote:> Your is fine, but it will be a little simpler if you use sapply() instead:
>
>> data.frame(Z=levels(myData$Z), CP=sapply(split(myData, myData$Z),
> +     function(x) crossprod(x[, 1], x[, 2])))
>   Z CP
> A A 10
> B B 10
>
> David C
>
>
> -----Original Message-----
> From: Gang Chen [mailto:gangchen6 at gmail.com]
> Sent: Wednesday, August 24, 2016 10:17 AM
> To: David L Carlson
> Cc: Jim Lemon; r-help mailing list
> Subject: Re: [R] aggregate
>
> Thank you all for the suggestions! Yes, I'm looking for the cross
> product between the two columns of X and Y.
>
> A follow-up question: what is a nice way to merge the output of
>
> lapply(split(myData, myData$Z), function(x) crossprod(x[, 1], x[, 2]))
>
> with the column Z in myData so that I would get a new dataframe as the
> following (the 2nd column is the cross product between X and Y)?
>
> Z   CP
> A   10
> B   10
>
> Is the following legitimate?
>
> data.frame(Z=levels(myData$Z), CP= unlist(lapply(split(myData,
> myData$Z), function(x) crossprod(x[, 1], x[, 2]))))
>
>
> On Wed, Aug 24, 2016 at 10:37 AM, David L Carlson <dcarlson at
tamu.edu> wrote:
>> Thank you for the reproducible example, but it is not clear what cross
product you want. Jim's solution gives you the cross product of the 2-column
matrix with itself. If you want the cross product between the columns you need
something else. The aggregate function will not work since it will treat the
columns separately:
>>
>>> A <- as.matrix(myData[myData$Z=="A", 1:2])
>>> A
>>   X Y
>> 1 1 4
>> 2 2 3
>>> crossprod(A) # Same as t(A) %*% A
>>    X  Y
>> X  5 10
>> Y 10 25
>>> crossprod(A[, 1], A[, 2]) # Same as t(A[, 1] %*% A[, 2]
>>      [,1]
>> [1,]   10
>>>
>>> # For all the groups
>>> lapply(split(myData, myData$Z), function(x) crossprod(as.matrix(x[,
1:2])))
>> $A
>>    X  Y
>> X  5 10
>> Y 10 25
>>
>> $B
>>    X  Y
>> X 25 10
>> Y 10  5
>>
>>> lapply(split(myData, myData$Z), function(x) crossprod(x[, 1], x[,
2]))
>> $A
>>      [,1]
>> [1,]   10
>>
>> $B
>>      [,1]
>> [1,]   10
>>
>> -------------------------------------
>> David L Carlson
>> Department of Anthropology
>> Texas A&M University
>> College Station, TX 77840-4352
>>
>>
>> -----Original Message-----
>> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Jim
Lemon
>> Sent: Tuesday, August 23, 2016 6:02 PM
>> To: Gang Chen; r-help mailing list
>> Subject: Re: [R] aggregate
>>
>> Hi Gang Chen,
>> If I have the right idea:
>>
>> for(zval in levels(myData$Z))
>>
crossprod(as.matrix(myData[myData$Z==zval,c("X","Y")]))
>>
>> Jim
>>
>> On Wed, Aug 24, 2016 at 8:03 AM, Gang Chen <gangchen6 at
gmail.com> wrote:
>>> This is a simple question: With a dataframe like the following
>>>
>>> myData <- data.frame(X=c(1, 2, 3, 4), Y=c(4, 3, 2, 1),
Z=c('A', 'A', 'B', 'B'))
>>>
>>> how can I get the cross product between X and Y for each level of
>>> factor Z? My difficulty is that I don't know how to deal with
the fact
>>> that crossprod() acts on two variables in this case.
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more,
see
>>> 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.
>>
>> ______________________________________________
>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> 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.

R help - Aug 2016 - aggregate

[R] aggregate

[R] aggregate

[R] aggregate