R help - Jul 2009 - Deos anyone know of a summary of conformability rules? along with a specific problem

The rules for  conformability of objects required for various operators remain a
mystery as do some related problems like the rules for recycling in creating
arrays etc. Would someone be able to direct me to where such rules are stated?

    In a related vein, there are all manner of operations that are readily coded
in Gauss or in MATA that fail, often mysteriously, in R. Are there some
guidelines available?

    And here is a specific problem:

         I would like to carry out logical comparisons between a (vector?) of
length EYE and each row of a JAY by EYE object, obtaining a conforming JAY by
EYE result of comparisons such as  Obj[Jay,Eye] == Vec[Eye]

    Any thoughts on how to effect this would be welcome.

    Among many failed efforts,

    as.matrix(7 element Vec) == { an 8 row, 7 column data.frame}  

            yields a 8 by 7 result

        v1 vs Ob[1,1]      v2 vs Obj[1,2]   ...
        v2 vs Ob[2,1]           .
         .                        et cetera
         .
        v7 vs Obj[7,1]
        v1  vs Obj[8,1] 

while
    as.matrix(7 element Vec) == t{ the 8 row, 7 column data.frame}  yields a
conformability error.

Thanks for any help or comments.
	[[alternative HTML version deleted]]

Steven Rytina wrote:
>     The rules for  conformability of objects required for various operators
remain a mystery as do some related problems like the rules for recycling in
creating arrays etc. Would someone be able to direct me to where such rules are
stated?
> 
>     In a related vein, there are all manner of operations that are readily
coded in Gauss or in MATA that fail, often mysteriously, in R. Are there some
guidelines available?
> 
>     And here is a specific problem:
> 
>          I would like to carry out logical comparisons between a (vector?)
of length EYE and each row of a JAY by EYE object, obtaining a conforming JAY by
EYE result of comparisons such as  Obj[Jay,Eye] == Vec[Eye]
> 
>     Any thoughts on how to effect this would be welcome.
> 
>     Among many failed efforts,
> 
>     as.matrix(7 element Vec) == { an 8 row, 7 column data.frame}  
> 
>             yields a 8 by 7 result
> 
>         v1 vs Ob[1,1]      v2 vs Obj[1,2]   ...
>         v2 vs Ob[2,1]           .
>          .                        et cetera
>          .
>         v7 vs Obj[7,1]
>         v1  vs Obj[8,1] 
> 
> while
>     as.matrix(7 element Vec) == t{ the 8 row, 7 column data.frame}  yields
a conformability error.
> 
> Thanks for any help or comments.
Not sure what the actual rule set (much less the rationale) is, but the 
thing that seems to be happening is that

(a) comparisons and other operations between matrices require strict 
conformance of dimensions. I.e. you cannot compare a 7x1 matrix to a 7x8 
one.

(b) comparisons of data frames to vectors removes any dimension 
attribute from the latter. So you can happily do

as.matrix(1:8,2,4)==as.data.frame(matrix(1:8,8,7)

but neither

as.matrix(1:7)==matrix(1:8,7,8)
nor
as.matrix(1:7)==matrix(1:8,8,7)

Transposing a data frame converts it to a matrix, so rule (a) kills you.

What you can do is either drop the as.matrix() stuff so that you compare 
the transposed data frame to a vector, or (preferably) use a construct like

sweep(D, V, 2, "==")



-- 
    O__  ---- Peter Dalgaard             ?ster Farimagsgade 5, Entr.B
   c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
  (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)              FAX: (+45) 35327907

On Jul 3, 2009, at 1:29 PM, Steven Rytina wrote:
>    The rules for  conformability of objects required for various  
> operators remain a mystery as do some related problems like the  
> rules for recycling in creating arrays etc. Would someone be able to  
> direct me to where such rules are stated?
>
>    In a related vein, there are all manner of operations that are  
> readily coded in Gauss or in MATA that fail, often mysteriously, in  
> R. Are there some guidelines available?
Not sure. Haven't seen any. Generally the complaint posted here is  
that R is not Matlab. Here is one professor's answer to that one:

http://germain.its.maine.edu/~hiebeler/comp/matlabR.pdf
>
>    And here is a specific problem:
>
>         I would like to carry out logical comparisons between a  
> (vector?) of length EYE and each row of a JAY by EYE object,  
> obtaining a conforming JAY by EYE result of comparisons such as   
> Obj[Jay,Eye] == Vec[Eye]
>
>    Any thoughts on how to effect this would be welcome.
 > i =10; j=4
 > vi <- 1:10
 > mji <- matrix(1:40, nrow=j)
 > matrix( mapply("==", vi,  mji[1:nrow(mji), ] ),
             nrow=nrow(mji) , byrow=TRUE)

       [,1]  [,2]  [,3]  [,4]  [,5]  [,6]  [,7]  [,8]  [,9] [,10]
[1,]  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE
[2,] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
[3,] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
[4,] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE

The fact that you have reversed the conventional order (for R anyway)  
of the indices makes me wonder it that is a source of confusion. You  
may have had problems in constructing an appropriate iterative row- 
wise comparison if you did not realize that the default order that  
matrix elements are filled and accessed is column-wise. The result of  
the mapply is just a long vector (and vi gets recycled)  so it needs  
to be hammered back into conformance to get what you specified.
>
>    Among many failed efforts,
>
>    as.matrix(7 element Vec) == { an 8 row, 7 column data.frame}
>
>            yields a 8 by 7 result
>
>        v1 vs Ob[1,1]      v2 vs Obj[1,2]   ...
>        v2 vs Ob[2,1]           .
>         .                        et cetera
>         .
>        v7 vs Obj[7,1]
>        v1  vs Obj[8,1]
>
> while
>    as.matrix(7 element Vec) == t{ the 8 row, 7 column data.frame}   
> yields a conformability error.
>
> Thanks for any help or comments.
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
David Winsemius, MD
Heritage Laboratories
West Hartford, CT