Re: [R] Converting Data Types

From: Martin Maechler <maechler_at_stat.math.ethz.ch>
Date: Wed, 21 May 2008 09:31:20 +0200

>>>>> "EW" == Edward Wijaya <ewijaya_at_gmail.com> >>>>> on Wed, 21 May 2008 11:52:17 +0900 writes:

    EW> Hi Peter,
    EW> Thanks.

    EW> as.matrix() does the trick.

and ... again my perennial remark to the above "trick" :

Do use data.matrix(dd) instead of

              as.matrix(dd)

if dd is a data frame ... it will also produce a numeric matrix when dd contains factor (and similar) columns.

Martin Maechler, ETH Zurich

    EW> - Edward

    EW> On Wed, May 21, 2008 at 11:31 AM, Peter Alspach     EW> <PAlspach_at_hortresearch.co.nz> wrote:

    >> Edward
    >> 
    >> Are you sure mymatrix is, in fact, a matrix and note a dataframe (which
    >> is a list)?  I get:
    >> 

>>> is.matrix(mymatrix)
    >> [1] FALSE

>>> is.data.frame(mymatrix)
    >> [1] TRUE

>>> samples <- mymatrix[1,]
>>> llgm <- dgamma(samples, scale=1, shape=2, log = TRUE)
    >> Error in dgamma(x, shape, scale, log) :
    >> Non-numeric argument to mathematical function
    >> 
    >> That is, the same error as you when mymatrix is a dataframe.  But
    >> convert it to a matrix and:
    >> 

>>> mymatrix <- as.matrix(mymatrix)
>>> is.matrix(mymatrix)
    >> [1] TRUE

>>> is.data.frame(mymatrix)
    >> [1] FALSE

>>> samples <- mymatrix[1,]
>>> llgm <- dgamma(samples, scale=1, shape=2, log = TRUE)
>>> llgm
    >> V1         V2         V3         V4         V5         V6
    >> -99.25657  -84.01700 -237.40735 -201.26922 -170.53122 -159.29770
    >> 
    >> HTH ....
    >> 
    >> Peter Alspach
    >> 
    >> 

>>> -----Original Message-----
>>> From: r-help-bounces_at_r-project.org
>>> [mailto:r-help-bounces_at_r-project.org] On Behalf Of Edward Wijaya
>>> Sent: Wednesday, 21 May 2008 2:17 p.m.
>>> To: r-help_at_r-project.org
>>> Subject: [R] Converting Data Types
>>>
>>> Hi,
>>>
>>> How can I convert the matrices to list.
>>>
>>> For example I have this snippet:
>>>
>>> samples<-mymatrix[1,]
>>> print(samples)
>>>
>>> which prints:
>>>
>>> V1 V2 V3 V4 V5 V6
>>> 1 103.9 88.5 242.9 206.6 175.7 164.4
>>>
>>>
>>> How can I convert the object "samples" such that it prints:
>>> [1] 103.9 88.5 242.9 206.6 175.7 164.4
>>>
>>> The reason I ask this because I can't use the former
>>> "samples" object with this function:
>>>
>>> llgm <- dgamma(samples, scale=1, shape=2, log = TRUE)
>>>
>>> which gives this error:
>>> e 1374Error in dgamma(x, shape, scale, log) :
>>> Non-numeric argument to mathematical function
>>>
>>> Regards,
>>> Edward
>>>
>>> ______________________________________________
>>> R-help_at_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.
>>>
    >> 
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    EW> ______________________________________________
    EW> R-help_at_r-project.org mailing list
    EW> https://stat.ethz.ch/mailman/listinfo/r-help
    EW> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html     EW> and provide commented, minimal, self-contained, reproducible code.

R-help_at_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. Received on Wed 21 May 2008 - 07:34:40 GMT

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