[Rcpp-devel] data.frame from R to C++?
deqiangs at bcm.edu
Tue Apr 12 12:38:09 CEST 2011
How should I read the txt in the following context?
The code I have is
RInside R(argc, argv);
std::string txt = "a=read.csv('xxx.xls',sep='\t',head=F)";
ans = R.parseEval(txt);
Rcpp::StringVector x1 = DF["V1"];
Rcpp::StringVector x2 = DF["V2"];
But the print of x1 and x2 is
What's wrong with my code?
On Apr 12, 2011, at 4:14 AM, Romain Francois wrote:
> Le 12/04/11 10:57, deqiang sun a écrit :
>> Hi Dirk,
>> Thanks very much for your example. From this example I learned how to passing data back and forth between R and C++.
>> The example is R code and uses piece of C++ code in side R program.
>> Well, it's better if you put this example(by only making slight changes to make R embeded in C++) inside package RInside.
>> Accessing data by column name is the feature I ( and other people) usually want.
>> However, is there a way to access the data Frame by row number?
> No. You access the column, and then do whatever with each element, as in
> Dirk's example.
>> On Apr 8, 2011, at 9:56 AM, Dirk Eddelbuettel wrote:
>>> Ok, I now committed a slightly nice example to RcppExamples, a package I
>>> should revamp to contain more examples. In there, we now receive a
>>> data.frame, operate on each column, create a new data and return old and new.
>>> The core of the code (inside the try/catch protection) is
>>> // construct the data.frame object
>>> Rcpp::DataFrame DF = Rcpp::DataFrame(Dsexp);
>>> // and access each column by name
>>> Rcpp::IntegerVector a = DF["a"];
>>> Rcpp::CharacterVector b = DF["b"];
>>> Rcpp::DateVector c = DF["c"];
>>> // do something
>>> a = 42;
>>> b = "foo";
>>> c = c + 7; // move up a week
>>> // create a new data frame
>>> Rcpp::DataFrame NDF =
>>> // and return old and new in list
>>> Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com
> Romain Francois
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