r data structures
To slightly correct what's been said: In general lists are linear objects, but a list can have dimension. An example is in Circle 8.1.8 of 'The R Inferno'. http://www.burns-stat.com/pages/Tutor/R_inferno.pdf Pat
On 16/08/2012 21:50, Schumacher, Jay S wrote:
are these correct/accurate/sensible statements: a vector is a one dimensional object. a matrix is a two dimensional object. a list is a one dimensional object. i'm working from this web page: http://www.agr.kuleuven.ac.be/vakken/statisticsbyR/someDataStructures.htm ----------------------------------------------------------------- On Aug 16, 2012, at 11:49 AM, Schumacher, Jay S wrote:
hi, i'm trying to understand r data structures. i see that vectors, matrix, factors and arrays have a "dimension." there seems to be no mention of dimensionality anywhere for lists or dataframes. can i consider lists and frames to be of fixed dimension 2?
About half of what you have deduced is wrong. Matrices, arrays, and dataframes do have dimensions, at least in technical R parlance, namely they have an attribute which can be queried with dim(). By definition matrices and dataframes have 2 dimensions. Arrays and matrices can be redimensioned, but dataframes cannot. Factors, lists, and atomic vectors do not have "dimensions", but they do have "lengths". An appropriately structured list (one with vectors all the same length) can be coerced to a dataframe with as.data.frame().
Patrick Burns pburns at pburns.seanet.com twitter: @portfolioprobe http://www.portfolioprobe.com/blog http://www.burns-stat.com (home of 'Some hints for the R beginner' and 'The R Inferno')