Yes, that's what I meant. Try selecting first and last n rows from data frame. Actually R's indexing ([) is very lax and can trump people (at least it has me) in strange ways. http://adv-r.had.co.nz/Subsetting.html How about subsetting with floats? J raises 'domain error'...R does...<quote>Numeric values are coerced to integer as by 'as.integer' (and hence truncated towards zero).</quote> I know this because I've made this mistake a couple of times!
One of the things that I really like about J is how regular it is....at least after you get *slightly more* comfortable with it. On Tue, Sep 2, 2014 at 3:00 PM, Devon McCormick <[email protected]> wrote: > I think he means this by "mixing +ve and -ve": > 0 1 _2 _1 { i.10 > 0 1 8 9 > > > On Tue, Sep 2, 2014 at 2:50 PM, Joe Bogner <[email protected]> wrote: > > > I also use { extensively (dyadic). I appreciate the challenge of > > coming up with a minimal list. One criteria may be: can it be done > > relatively easily with one of the other operations? > > > > For {, it's fairly easy to use {. and }.... > > > > For example: {. 3 }. 0 1 2 3 4 5 > > > > With a trivial case, the performance is negligible, but perhaps not as > > readable > > > > 100 timespacex '{. 9999999 }. i. 1e7' > > 0.0248935 1.3422e8 > > > > 100 timespacex '9999999 { i. 1e7' > > 0.0269468 1.3422e8 > > > > I mostly use it for simple indexing. I didn't understand your comment > > about mixing +ve and -ve. Can you elaborate? > > > > [by the way, excellent list Devon. I may use it to extend my > > coffeescript implementation of APL to have functioning examples for > > each of those operations] > > > > > > > > On Tue, Sep 2, 2014 at 2:39 PM, Vijay Lulla <[email protected]> > wrote: > > > Just out of curiosity, why is { not included? I use it extensively for > > my J > > > explorations. Also, it is much more regular and useful(flexible?) than > > > indexing in other languages. For e.g., You cannot mix +ve and -ve > indexes > > > in R but it works as expected (at least for me) in J. Regardless, nice > > work. > > > > > > Thanks, > > > Vijay. > > > > > > > > > On Tue, Sep 2, 2014 at 1:16 PM, Devon McCormick <[email protected]> > > wrote: > > > > > >> Based on Skip's suggestion, this page is now here - > > >> http://www.jsoftware.com/jwiki/DevonMcCormick/MinimalBeginningJ - and > > is > > >> titled "Minimal J for Beginners". > > >> > > >> > > >> On Tue, Sep 2, 2014 at 1:10 PM, Devon McCormick <[email protected]> > > >> wrote: > > >> > > >> > Good point - I picked up the "J Kernel" label from the discussion. > > >> > > > >> > > > >> > On Tue, Sep 2, 2014 at 12:36 PM, Skip Cave <[email protected] > > > > >> > wrote: > > >> > > > >> >> Devon, nice job of putting together a reduced set of primitives for > > rhe > > >> >> beginner. The only issue I see is the name. As a beginner, I would > > never > > >> >> think to find a set of most-commonly-used primitives under the name > > "J > > >> >> Kernel" That actually sounds like a discussion of the internals of > J, > > >> >> which > > >> >> is what I thought when I read the subject of your email. I doubt > > that a > > >> >> beginner would check out a page with that label. A title like "J's > > Basic > > >> >> Commands for Beginners" or equivalent, would be more likely to > > attract > > >> the > > >> >> intended audience. > > >> >> > > >> >> Skp > > >> >> > > >> >> Skip Cave > > >> >> Cave Consulting LLC > > >> >> > > >> >> > > >> >> On Tue, Sep 2, 2014 at 9:54 AM, Devon McCormick < > [email protected]> > > >> >> wrote: > > >> >> > > >> >> > Based on some feedback from Greg Borota last year on his > > experiences > > >> >> > learning J, I've put together a page on the J Wiki - > > >> >> > http://www.jsoftware.com/jwiki/DevonMcCormick/JKernel - that > has a > > >> few > > >> >> > selected things from J on which a beginner can concentrate to > avoid > > >> >> being > > >> >> > overwhelmed by the language in full. > > >> >> > > > >> >> > It's a pretty bare minimum and I couldn't find a good link that > > >> explains > > >> >> > J's use of single quote for quoted strings but everyone should > feel > > >> >> free to > > >> >> > add to it - sparingly, as it's supposed to be a reduced set of > the > > >> >> > language. > > >> >> > > > >> >> > It might make sense to leave the existing page much as it is and > to > > >> >> think > > >> >> > about a 2nd tier of slightly more advanced verbs and such. There > > were > > >> >> good > > >> >> > suggestions in the original discussion - > > >> >> > > > >> >> > > > >> >> > > >> > > > http://jsoftware.2058.n7.nabble.com/Learning-J-language-initial-thoughts-td52786.html#a52793 > > >> >> > - that I elided as I consider them more than the bare minimum > > (things > > >> >> like > > >> >> > rank modifiers and logic verbs). > > >> >> > > > >> >> > -- > > >> >> > Devon McCormick, CFA > > >> >> > > > ---------------------------------------------------------------------- > > >> >> > For information about J forums see > > >> http://www.jsoftware.com/forums.htm > > >> >> > > > >> >> > > ---------------------------------------------------------------------- > > >> >> For information about J forums see > > http://www.jsoftware.com/forums.htm > > >> >> > > >> > > > >> > > > >> > > > >> > -- > > >> > Devon McCormick, CFA > > >> > > > >> > > > >> > > >> > > >> -- > > >> Devon McCormick, CFA > > >> ---------------------------------------------------------------------- > > >> 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 > > > > > > -- > Devon McCormick, CFA > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
