<div dir="ltr">Hello, <br>I thought I'd also chip-in my thoughts to eddi's feature request. <br>Short answer: I don't think this feature is necessary. I basically agree with mnel's reply. <br>Long answer: My argument goes along these lines (in addition to the S3/S4 methods mnel mentions). If you for example type `[.data.frame` in your R-session, you'd see this snippet:<br>
<br> if (is.matrix(i)) <br> return(as.matrix(x)[i])<br><br>That is, if you do: <br><br> df <- data.frame(x=1:5, y=1:5, z=1:5)<br> mm <- matrix(1:12, ncol=3)<br> df[mm] # gives<br> [1] 1 2 3 4 5 1 2 3 4 5 1 2<br>
<br> df <- data.frame(x=1:2, y=1:2, z=1:2)<br> df[mm] # gives<br> [1] 1 2 1 2 1 2 NA NA NA NA NA NA<br><br>Here, the indexing is a matrix. It's obvious. Now, should this behaviour be changed because people would be confused that subsetting a data.frame resulted in a vector? Or because it's not user friendly? Even better, try out `df[mm, ]`. If `i` is a matrix, this is what the code does. I am not convinced this is "bad" design. Functions take arguments of different types ALL the time and they return outputs *depending on the type of input*. This is why I am not sold on the point of "bad design". It's essential to know the type of objects `i` can take and *understand* it. <br>
<br>If a function is designed that takes several types of objects for `i` and their behaviour is documented, and the documented behaviour is consistent, then I can't accept there's a problem. <br><br>I agree there are people who don't read the manual and "try" things out. But they are going to have problems with every other function in R. <br>
<br>For example, "unstack" is a function for which same input type gives different output type. That is, it provides a data.frame if the columns are equal after unstaking and list if they are not. That is, compare the outputs of:<br>
<br> df <- data.frame(x=rep(1:3, each=3), y=1:9)<br> unstack(df, y ~ x)<br><br>with<br><br> df <- data.frame(x=c(rep(1:3, each=3), 3), y=1:10)<br> unstack(df, y ~ x)<br><br>But if people don't read the documentation, they wouldn't know this difference until they land up on errors. Now, making it user-friendly would mean that it "always" returns a list. <br>
<br>Now, is this "bad" design because it gives two object types for same input? Does it require a change? I personally don't think so.<br><br>To sum up, what eddi points out as "not being user-friendly" (or arguably "bad design") is everywhere inside R if you look closely. My view is that it's very clear that there should be some effort in understanding a function before using it. Not all functions are plain simple. Some functions have exceptions and some packages have a steep learning curve.<br>
<br>Best,<br>Arun.<br><br><br>On Sat, Apr 27, 2013 at 12:00 PM, <<a href="mailto:datatable-help-request@lists.r-forge.r-project.org">datatable-help-request@lists.r-forge.r-project.org</a>> wrote:<br>><br>> Send datatable-help mailing list submissions to<br>
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><br>> or, via email, send a message with subject or body 'help' to<br>> <a href="mailto:datatable-help-request@lists.r-forge.r-project.org">datatable-help-request@lists.r-forge.r-project.org</a><br>
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> than "Re: Contents of datatable-help digest..."<br>><br>><br>> Today's Topics:<br>><br>> 1. Re: changing data.table by-without-by syntax to require a<br>> "by" (Frank Erickson)<br>
> 2. Re: variable column names (Sam Steingold)<br>> 3. Re: variable column names (Matthew Dowle)<br>> 4. Re: changing data.table by-without-by syntax to require a<br>> "by" (Matthew Dowle)<br>
> 5. Re: variable column names (Victor Kryukov)<br>><br>><br>> ----------------------------------------------------------------------<br>><br>> Message: 1<br>> Date: Fri, 26 Apr 2013 15:34:39 -0500<br>
> From: Frank Erickson <<a href="mailto:FErickson@psu.edu">FErickson@psu.edu</a>><br>> To: "data.table source forge"<br>> <<a href="mailto:datatable-help@lists.r-forge.r-project.org">datatable-help@lists.r-forge.r-project.org</a>><br>
> Subject: Re: [datatable-help] changing data.table by-without-by syntax<br>> to require a "by"<br>> Message-ID:<br>> <CAJd-hdkv1oiSjfA625oBxmXwr5YuVUzz==<a href="mailto:3GLaWJTakAtzMJVw@mail.gmail.com">3GLaWJTakAtzMJVw@mail.gmail.com</a>><br>
> Content-Type: text/plain; charset="iso-8859-1"<br>><br>> I disagree with the criticism of data.table's complexity (in the OP).<br>> There's nothing wrong with overloading the syntax (that is what CS people<br>
> call it, right?). As long as Matthew's in control of it, it's likely to<br>> have some internal consistency (which, of course, he could explain).<br>> However, I like the suggestion to add options (defaulting to something<br>
> globally adjustable) to disable some of the overloading. Along similar<br>> lines (I think), I find unique.data.table very unintuitive. I can see how<br>> it could be useful, but strongly prefer base::unique for my current<br>
> applications.<br>><br>> Anyway, I have nothing particular to say about the piece of syntax you all<br>> are currently discussing. I just registered with this list to chime in<br>> here, instead of further cluttering SO (where eddi answered one of my<br>
> questions yesterday). These emails sure are wide; must be like 1500px!<br>> Interesting to try out this ancient mailing-list form of communication.<br>> Please let me know if I should be using "Reply All" or actually quoting<br>
> that massive thread (as everyone else seems to be doing with each post).<br>><br>> Frank<br>> -------------- next part --------------<br>> An HTML attachment was scrubbed...<br>> URL: <<a href="http://lists.r-forge.r-project.org/pipermail/datatable-help/attachments/20130426/eb6556ae/attachment-0001.html">http://lists.r-forge.r-project.org/pipermail/datatable-help/attachments/20130426/eb6556ae/attachment-0001.html</a>><br>
><br>> ------------------------------<br>><br>> Message: 2<br>> Date: Fri, 26 Apr 2013 18:02:31 -0400<br>> From: Sam Steingold <<a href="mailto:sds@gnu.org">sds@gnu.org</a>><br>> To: <a href="mailto:datatable-help@lists.r-forge.r-project.org">datatable-help@lists.r-forge.r-project.org</a><br>
> Subject: Re: [datatable-help] variable column names<br>> Message-ID: <<a href="mailto:87wqrpj6h4.fsf@gnu.org">87wqrpj6h4.fsf@gnu.org</a>><br>> Content-Type: text/plain<br>><br>> > * Sam Steingold <fqf@tah.bet> [2013-04-26 13:05:39 -0400]:<br>
> ><br>> >> * Matthew Dowle <zqbjyr@zqbjyr.cyhf.pbz> [2013-04-26 17:45:53 +0100]:<br>> >><br>> >> S.O. is probably better for this kind of question then.<br>> >> But if you don't get an answer there, then come back to datatable-help.<br>
> ><br>> > <a href="http://stackoverflow.com/questions/16241687/summarize-a-data-table-across-multiple-columns">http://stackoverflow.com/questions/16241687/summarize-a-data-table-across-multiple-columns</a><br>
><br>> downvoted, unlikely to be answered.<br>><br>> --<br>> Sam Steingold (<a href="http://sds.podval.org/">http://sds.podval.org/</a>) on Ubuntu 12.10 (quantal) X 11.0.11300000<br>> <a href="http://www.childpsy.net/">http://www.childpsy.net/</a> <a href="http://iris.org.il">http://iris.org.il</a> <a href="http://think-israel.org">http://think-israel.org</a><br>
> <a href="http://americancensorship.org">http://americancensorship.org</a> <a href="http://pmw.org.il">http://pmw.org.il</a> <a href="http://mideasttruth.com">http://mideasttruth.com</a><br>> We have preferences. You have biases. They have prejudices.<br>
><br>><br>><br>> ------------------------------<br>><br>> Message: 3<br>> Date: Fri, 26 Apr 2013 23:47:55 +0100<br>> From: Matthew Dowle <<a href="mailto:mdowle@mdowle.plus.com">mdowle@mdowle.plus.com</a>><br>
> To: <<a href="mailto:sds@gnu.org">sds@gnu.org</a>><br>> Cc: <a href="mailto:datatable-help@lists.r-forge.r-project.org">datatable-help@lists.r-forge.r-project.org</a><br>> Subject: Re: [datatable-help] variable column names<br>
> Message-ID: <<a href="mailto:30d6ae8f1a0d6974ebbd54da0d86f3b2@imap.plus.net">30d6ae8f1a0d6974ebbd54da0d86f3b2@imap.plus.net</a>><br>> Content-Type: text/plain; charset=UTF-8; format=flowed<br>><br>> On 26.04.2013 23:02, Sam Steingold wrote:<br>
> >> * Sam Steingold <fqf@tah.bet> [2013-04-26 13:05:39 -0400]:<br>> >><br>> >>> * Matthew Dowle <zqbjyr@zqbjyr.cyhf.pbz> [2013-04-26 17:45:53<br>> >>> +0100]:<br>> >>><br>
> >>> S.O. is probably better for this kind of question then.<br>> >>> But if you don't get an answer there, then come back to<br>> >>> datatable-help.<br>> >><br>> >><br>
> >> <a href="http://stackoverflow.com/questions/16241687/summarize-a-data-table-across-multiple-columns">http://stackoverflow.com/questions/16241687/summarize-a-data-table-across-multiple-columns</a><br>> ><br>
> > downvoted, unlikely to be answered.<br>><br>> I've read it through.<br>><br>> Perhaps sleep on it, don't look for 24hrs and look again as if you were<br>> trying to answer it yourself. Are there any small changes you can make<br>
> to make it easier to answer? It wasn't me that downvoted but I suspect<br>> it's been done to encourage you to improve the question. Downvotes can<br>> (and often are) reversed. I've had many more downvotes than you once,<br>
> but then I improved it and it went to +10.<br>><br>> And, it's Friday and we've all had a long week!<br>><br>> Matthew<br>><br>><br>><br>><br>> ------------------------------<br>><br>
> Message: 4<br>> Date: Sat, 27 Apr 2013 00:35:17 +0100<br>> From: Matthew Dowle <<a href="mailto:mdowle@mdowle.plus.com">mdowle@mdowle.plus.com</a>><br>> To: Frank Erickson <<a href="mailto:FErickson@psu.edu">FErickson@psu.edu</a>><br>
> Cc: "data.table source forge"<br>> <<a href="mailto:datatable-help@lists.r-forge.r-project.org">datatable-help@lists.r-forge.r-project.org</a>><br>> Subject: Re: [datatable-help] changing data.table by-without-by syntax<br>
> to require a "by"<br>> Message-ID: <<a href="mailto:be967ecd9c927ade15c15eb9985d919e@imap.plus.net">be967ecd9c927ade15c15eb9985d919e@imap.plus.net</a>><br>> Content-Type: text/plain; charset="utf-8"<br>
><br>><br>><br>> Thanks for your comments Frank.<br>><br>> Ha, yes it's ancient but still has<br>> a place. Yes "reply all": Back To: sender (if it's to someone in<br>> particular) and cc the list. But on general topics where lots of people<br>
> are on the thread, just To: datatable-help alone is fine. Personally I<br>> prefer "top posting". Like I'm doing now. I only scroll down if I need<br>> to. I didn't notice the history was building up. If you comment inline<br>
> later, then say "scroll down for comments inline" or something at the<br>> top. Note that Nabble collapses the history for you so threads are much<br>> easier to read there. Or I tend to read via RSS (gmane) in Outlook, so<br>
> it feels like an email inbox which turns bold on new posts. You only<br>> need to subscribe to post (spam control). Most people turn off mail<br>> delivery pretty quickly I imagine (or setup an auto rule to move into a<br>
> folder, but then you might as well subscribe to RSS I guess).<br>><br>> S.O. is<br>> quite strict: must be clear questions with a clear answer, only one of<br>> which can be accepted. No opinion, voting, discussing or notices (enter<br>
> mailing lists). Chat room is good but for quick chat when people are in<br>> the room at the same time. Many companies (sensibly) block chat access,<br>> though. Mailing lists allows all timezones a chance at a slower pace.<br>
> Anonymity is just as acceptable and as easy in both places.<br>><br>> Matthew<br>><br>><br>> On 26.04.2013 21:34, Frank Erickson wrote:<br>><br>> > I disagree with the<br>> criticism of data.table's complexity (in the OP). There's nothing wrong<br>
> with overloading the syntax (that is what CS people call it, right?). As<br>> long as Matthew's in control of it, it's likely to have some internal<br>> consistency (which, of course, he could explain). However, I like the<br>
> suggestion to add options (defaulting to something globally adjustable)<br>> to disable some of the overloading. Along similar lines (I think), I<br>> find unique.data.table very unintuitive. I can see how it could be<br>
> useful, but strongly prefer base::unique for my current applications.<br>> ><br>> Anyway, I have nothing particular to say about the piece of syntax you<br>> all are currently discussing. I just registered with this list to chime<br>
> in here, instead of further cluttering SO (where eddi answered one of my<br>> questions yesterday). These emails sure are wide; must be like 1500px!<br>> Interesting to try out this ancient mailing-list form of communication.<br>
> Please let me know if I should be using "Reply All" or actually quoting<br>> that massive thread (as everyone else seems to be doing with each post).<br>><br>> > Frank<br>><br>><br>> -------------- next part --------------<br>
> An HTML attachment was scrubbed...<br>> URL: <<a href="http://lists.r-forge.r-project.org/pipermail/datatable-help/attachments/20130427/260f3119/attachment-0001.html">http://lists.r-forge.r-project.org/pipermail/datatable-help/attachments/20130427/260f3119/attachment-0001.html</a>><br>
><br>> ------------------------------<br>><br>> Message: 5<br>> Date: Fri, 26 Apr 2013 16:42:04 -0700<br>> From: Victor Kryukov <<a href="mailto:victor.kryukov@gmail.com">victor.kryukov@gmail.com</a>><br>
> To: Matthew Dowle <<a href="mailto:mdowle@mdowle.plus.com">mdowle@mdowle.plus.com</a>><br>> Cc: <a href="mailto:datatable-help@lists.r-forge.r-project.org">datatable-help@lists.r-forge.r-project.org</a>, <a href="mailto:sds@gnu.org">sds@gnu.org</a><br>
> Subject: Re: [datatable-help] variable column names<br>> Message-ID:<br>> <CANJmMqTz5+6djLEwpZxsub6LB=3L37=JB3xt5AhG1XgWG=<a href="mailto:nJgw@mail.gmail.com">nJgw@mail.gmail.com</a>><br>> Content-Type: text/plain; charset=ISO-8859-1<br>
><br>> On Fri, Apr 26, 2013 at 3:47 PM, Matthew Dowle <<a href="mailto:mdowle@mdowle.plus.com">mdowle@mdowle.plus.com</a>> wrote:<br>> > On 26.04.2013 23:02, Sam Steingold wrote:<br>> >>> <a href="http://stackoverflow.com/questions/16241687/summarize-a-data-table-across-multiple-columns">http://stackoverflow.com/questions/16241687/summarize-a-data-table-across-multiple-columns</a><br>
> >><br>> >> downvoted, unlikely to be answered.<br>> ><br>> > I've read it through.<br>> ><br>> > Perhaps sleep on it, don't look for 24hrs and look again as if you were<br>
> > trying to answer it yourself. Are there any small changes you can make to<br>> > make it easier to answer? It wasn't me that downvoted but I suspect it's<br>> > been done to encourage you to improve the question. Downvotes can (and often<br>
> > are) reversed. I've had many more downvotes than you once, but then I<br>> > improved it and it went to +10.<br>> ><br>> > And, it's Friday and we've all had a long week!<br>><br>
> Beautiful advice, Matthew!<br>><br>> Sam - I've provided my answer (and even used Reduce since you seem to<br>> be coming from Lisp land), but I also think some of the down<br>> votes/comments have their merit.<br>
><br>><br>> ------------------------------<br>><br>> _______________________________________________<br>> datatable-help mailing list<br>> <a href="mailto:datatable-help@lists.r-forge.r-project.org">datatable-help@lists.r-forge.r-project.org</a><br>
> <a href="https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help">https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help</a><br>><br>> End of datatable-help Digest, Vol 38, Issue 26<br>
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