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 <vijaylu...@gmail.com> 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 <erl...@erlinghellenas.se> > 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 > vlu...@iupui.edu > > <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
