[R] data manipulation between vector and matrix

[arun]

Hi,

By comparing the different methods:
set.seed(5)
 mat1<-matrix(sample(1:1e6,1e6,replace=TRUE),ncol=10000)
 set.seed(25)
 x<-sample(1:1e6,10000,replace=TRUE)
 system.time(z1<-sweep(-mat1,2,x,"+"))
#   user  system elapsed 
 # 0.076   0.000   0.069 
 system.time(z2<-apply(-mat1,1,`+`,x))
 #  user  system elapsed 
 # 0.036   0.000   0.031 
 system.time(z3<-aaply(-mat1,1,`+`,x))
#   user  system elapsed 
#  1.880   0.000   1.704 
 system.time(z4<- x-t(mat1))  #winner
#   user  system elapsed 
 # 0.004   0.000   0.007 
 system.time(z5<- t(x-t(mat1)))
#   user  system elapsed 
#  0.008   0.000   0.009 


A.K.





________________________________
From: C W <tmrsg11 at gmail.com>
To: arun <smartpink111 at yahoo.com> 
Cc: R help <r-help at r-project.org>; Sarah Goslee <sarah.goslee at gmail.com> 
Sent: Wednesday, December 5, 2012 4:11 PM
Subject: Re: [R] data manipulation between vector and matrix


thanks, I knew about apply, but did not you you can put plus signs with quotes.  That's a cool tricky,
Mike


On Wed, Dec 5, 2012 at 4:05 PM, arun <smartpink111 at yahoo.com> wrote:

HI,
>In addition to ?sweep(), you can use
>
>apply(-mat,1,`+`,x)
>
>#or
>library(plyr)
>aaply(-mat,1,"+",x)
>
>
>A.K.
>
>
>
>
>
>
>
>----- Original Message -----
>From: C W <tmrsg11 at gmail.com>
>To: Sarah Goslee <sarah.goslee at gmail.com>
>Cc: r-help <r-help at r-project.org>
>Sent: Wednesday, December 5, 2012 1:51 PM
>Subject: Re: [R] data manipulation between vector and matrix
>
>Thanks, Sarah.  First time heard about sweep(), it worked just the way I
>wanted.
>Mike
>
>On Wed, Dec 5, 2012 at 1:42 PM, Sarah Goslee <sarah.goslee at gmail.com> wrote:
>
>> Hi,
>>
>> On Wed, Dec 5, 2012 at 1:30 PM, C W <tmrsg11 at gmail.com> wrote:
>> > Dear list,
>> > I was curious how to subtract a vector from matrix?
>> >
>> > Say, I have
>> >
>> > mat <- matrix(1:40, nrow=20, ncol=2)
>> >
>> > x <-c(1,2)
>>
>> Thanks for the actual reproducible example.
>>
>> > I want,
>> >
>> > x-mat[1,] and x-mat[2,], and so on... Basically, subtract column elements
>> > of x against column elements in mat.
>> >
>> > But x-mat won't do it.
>>
>> This will (note the modification to get x - mat):
>> > sweep(-mat, 2, x, "+")
>>       [,1] [,2]
>>  [1,]    0  -19
>>  [2,]   -1  -20
>>  [3,]   -2  -21
>>  [4,]   -3  -22
>>  [5,]   -4  -23
>> etc.
>>
>> --
>> Sarah Goslee
>> http://www.functionaldiversity.org
>>
>
>    [[alternative HTML version deleted]]
>
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