Oops! I meant force to n by 1 by using (,@".);._2 z
I had shown 1 by n in previous post. On Sun, Apr 16, 2017 at 12:53 PM, chris burke <[email protected]> wrote: > Please feel free to ask such questions. This is the purpose of the forum. > > J does allow 1-column matrices, e.g. > > i.4 1 > 0 > 1 > 2 > 3 > > What is happening in your example is that you are reading in a table of > character data, where each row is the character string representing a > single number. The function ". is used to convert each string to a number. > If the result of executing such a string is a single number, then it is a > atom. If it is more than one number, it is a list, e.g. compare: > > ". '123' > 123 > $ ". '123' NB. atom > > > ". '123 45' > 123 45 > $ ". '123 45' NB. list > 2 > > Now when J executes each row of your table, it sees that every result is an > atom, and assembles the atoms into a list. If one or more result was itself > a list, the final assembly would be 2-dimensional. > > > On Sun, Apr 16, 2017 at 11:26 AM, Michael Goodrich < > [email protected]> wrote: > > > All, > > > > In using 'readtable' as defined in the primer I find the following > > situation: > > > > Reading in a square matrix from a file with each row of numbers on a > line I > > always get the 'correct' answer when asking about the shape of the read > in > > data, EXCEPT when the data has only one value per line ie is a vector or > > de-generate matrix if you will. In that case the shape comes back with a > > single number say N whereas I was expecting it to say 'N 1' and indeed > the > > read in data is not available for linear algebra operations whereas data > > with more that one column is without further ado. > > > > Why does J not treat a column of numbers as a N by 1 'matrix' ie a vector > > rather than a list? > > > > (Pardon me if I sound like I am whining ;-) > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
