[R] Converting Data Types

[Martin Maechler]

>>>>> "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.