My memory of grappling with the "how to handle missing data" issue in APL and J was that the most complete solution was to have a separate boolean array of the same shape as the data array that identified missings. This is certainly a clunkier approach from the user's POV compared to R, but is arguably less ambiguous and more powerful than defining a particular number as "missing" for a particular instance.
Perhaps an adverb/conjunction that filtered an array based on a missing array, prior to applying the desired operation would make life easier for users? On Thu, Sep 21, 2017 at 4:59 AM, Raul Miller <[email protected]> wrote: > I do not have any problem with using _ or _. or __ as placeholders > where you do not know what value to use. > > I do not think, however, that distinguishing between different kinds > of _. values is something we should have to deal with. > > Thanks, > > -- > Raul > > On Wed, Sep 20, 2017 at 11:04 AM, Vijay Lulla <[email protected]> > wrote: > > To answer Henry's question based on the behavior of R, which Erling > > advocates, and I too love!! > > > > In R, length of vector (what we'd call list in J) with missing values is > > still the actual number of elements in a vector. Missing value *is* > still > > a value in a list and it gets counted! However, it makes no sense to > take > > a mean/stddev/median unless we handle (acknowledge?) missing values so R > > will yield missing value (NA) when you take mean/stddev/median with a > > vector with missing values. Check out this behavior from an interactive > R > > session: > > > >> x <- 1:10 > >> x > > [1] 1 2 3 4 5 6 7 8 9 10 > >> x <- c(x,NA) > >> x > > [1] 1 2 3 4 5 6 7 8 9 10 NA > >> mean(x) > > [1] NA > >> mean(x, na.rm=TRUE) > > [1] 5.5 > >> length(x) > > [1] 11 > >> sd(x) > > [1] NA > >> median(x) > > [1] NA > >> > > > > IMO, this is a good practice (notice I didn't say right) and helps with > > dealing with issues in real world. No other language that I'm aware of > > deals with missing values so consistently, and pragmatically, as R. And > > oh, all of this is described quite clearly in the documentation for R. > > > > On Wed, Sep 20, 2017 at 10:51 AM, Erling Hellenäs < > [email protected]> > > wrote: > > > >> Hi all ! > >> > >> Here is part of the standard. Required exception handling. Things I > >> discuss in my post. Is it implemented in J? > https://en.wikipedia.org/wiki/ > >> IEEE_754#Exception_handling > >> The floating point standard is obviously used in environments where the > >> users can not afford random results, so there must be solutions to the > >> problems I mention, which we also can see in this wikipedia article. > >> > >> Cheers, > >> Erling > >> > >> > >> Den 2017-09-20 kl. 16:27, skrev Erling Hellenäs: > >> > >>> I hope others want to read my post even if Raul discards it as not > worthy > >>> of comments. /Erling > >>> > >>> > >>> Den 2017-09-20 kl. 12:25, skrev Raul Miller: > >>> > >>>> This isn't just J - this is the IEEE-754 floating point standard. > >>>> > >>>> It would be really nice if computers could deal with infinities, > >>>> instantly, at no cost. Sadly, though, that's not going to happen. > >>>> > >>>> FYI, > >>>> > >>>> > >>> ---------------------------------------------------------------------- > >>> For information about J forums see http://www.jsoftware.com/forums.htm > >>> > >> > >> ---------------------------------------------------------------------- > >> For information about J forums see http://www.jsoftware.com/forums.htm > >> > > > > > > > > -- > > Vijay Lulla, Ph.D. > > > > Assistant Professor, > > Dept. of Geography, > > Indiana University Purdue University Indianapolis (IUPUI) > > 425 University Blvd, CA-207C. > > Indianapolis, IN-46202 > > [email protected] > > > > <http://vijaylulla.com> > > http://vijaylulla.com > > ---------------------------------------------------------------------- > > 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
