[Rd] Manipulating R lists in C

[Tom McCallum]

Thank you so much!! - that works now.

Tom

On Fri, 17 Nov 2006 14:40:38 -0000, Roger Bivand <Roger.Bivand at nhh.no>  
wrote:

> On Fri, 17 Nov 2006, Tom McCallum wrote:
>
>> Hi,
>>
>> I have been studying the R manual on lists but cannot seem to create a
>> simple R list in C - I keep on getting "'dimnames' applied to non-array"
>> whenever I attempt to assign names to the list elements:
>
> Maybe:
>
>    setAttrib( priceList, R_NamesSymbol, dimnames );
>
> why should a list have dimnames?
>
> In addition, your dimnames is a list, and likely ought to be a character
> vector. That way you can get away with many fewer PROTECT().
>
> Roger
>
>>
>> Wanted output a list structure something like
>> 	[ type="Bid", price=2.0, volume=1000 ]
>>
>> I can get up to a list of
>> 	[ "Bid2, 2.0, 1000 ]
>>
>> But for the life of me I can't assign the names to the list items - any
>> suggestions?
>>
>> Below is what I already have - any comments on things I don't really  
>> need
>> to do as well in terms of creating extra string objects etc are also
>> helpful.
>>
>> Many thanks
>>
>> Tom
>>
>>
>> ======EXTRACT=========
>>
>>
>>    SEXP typeStr, volumeStr, priceStr, typeValStr;
>>    SEXP priceList;
>>
>>    // create main list of vectors (unspecific items )
>>    PROTECT( priceList = allocVector( VECSXP, 3 ) );
>>
>>    // for each item create a label and attach value
>>    PROTECT( typeValStr = allocVector( STRSXP, 1 ) );
>>    SET_STRING_ELT( typeValStr, 0,
>> mkChar( getPriceDataTypeAsString( p.getData().getType() ).c_str() ) );
>>    SET_STRING_ELT( priceList, 0, typeValStr) ;
>>
>>    SEXP priceSXP;
>>    PROTECT( priceSXP = allocVector( REALSXP, 1) );
>>    REAL(priceSXP)[0] = p.getData().getPrice();
>>    SET_VECTOR_ELT( priceList, 1, priceSXP);
>>
>>    SEXP volumeSXP;
>>    PROTECT( volumeSXP = allocVector( REALSXP, 1 ) );
>>    REAL(volumeSXP)[0] = p.getData().getVolume();
>>    SET_VECTOR_ELT( priceList, 2, volumeSXP);
>>
>>    ********WORKS UP TO HERE*************
>>
>>    // add the names of the list items (type,price,volume)
>>    SEXP dimnames;
>>    PROTECT( dimnames = allocVector( VECSXP, 3 ) );
>>
>>    // first create string objects
>>    PROTECT( typeStr = allocVector( STRSXP,1 ) );
>>    SET_STRING_ELT( typeStr, 0, mkChar("type") );
>>
>>    PROTECT( priceStr = allocVector( STRSXP,1 ) );
>>    SET_STRING_ELT( priceStr, 0, mkChar("price") );
>>
>>    PROTECT( volumeStr = allocVector( STRSXP,1 ) );
>>    SET_STRING_ELT( volumeStr, 0, mkChar("volume") );
>>
>>    // assign string objects to vector
>>    SET_VECTOR_ELT( dimnames, 0, typeStr );
>>    SET_VECTOR_ELT( dimnames, 1, priceStr);
>>    SET_VECTOR_ELT( dimnames, 2, volumeStr );
>>
>>    // assign vector to original list of data
>>    setAttrib( priceList, R_DimNamesSymbol, dimnames ); <----- I think  
>> this
>> is wrong but I don;t know what it should be
>>
>> ===========END EXTRACT===============
>>
>>
>



-- 
Dr. Thomas McCallum
Systems Architect,
Level E Limited
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Email: tom at levelelimited.com

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