Thank you all for answering such a newbie question. :) David thank you for your example too. Best wishes, I.S On Nov 14, 2015 18:28, "David L Carlson" <dcarl...@tamu.edu> wrote:
> My original answer works fine as long as fin_hyp contains only one > definition for the line, but if it contains more than one, R will use a > different line for each test which is probably not what you want (e.g. the > first point will be tested against the first line and the second point > against the second line, etc). In that case a loop or apply function would > be needed: > > > data <- data.frame(x = c(1,2,3,1,1,1), y = c(1,2,3,4,6,7)) > > fin_hyp <- data.frame(slope = c(2, 1, -2), constant = c(1, -1, 7)) > > outputs <- apply(fin_hyp, 1, function(z) data$y > z[1] * data$x + z[2]) > > outputs > [,1] [,2] [,3] > [1,] FALSE TRUE FALSE > [2,] FALSE TRUE FALSE > [3,] FALSE TRUE TRUE > [4,] TRUE TRUE FALSE > [5,] TRUE TRUE TRUE > [6,] TRUE TRUE TRUE > > The first column is the result for the first equation (row in fin_hyp) and > so on. > > David L. Carlson > Department of Anthropology > Texas A&M University > > > -----Original Message----- > From: David L Carlson > Sent: Saturday, November 14, 2015 9:57 AM > To: 'Duncan Murdoch' <murdoch.dun...@gmail.com>; Ilgaz S < > ilgaz.so...@gmail.com>; r-help@r-project.org > Subject: RE: [R] Suprising R behaviour > > You definitely need to learn about the differences between R and the other > languages that you are familiar with. You've done some work since you > mention the apply() family, but those are just another way of programming a > loop. In many cases (including this one), a loop is not needed. Here's your > code in a plain text message with some additions: > > data <- data.frame(x = c(1,2,3,1,1,1), y = c(1,2,3,4,6,7)) > # fin_hyp could just as easily be a data frame or a matrix > fin_hyp <- list(slope = 2, constant = 1) > # R vectorizes the following command and automatically computes the > # result for each row in "data" > outputs <- data['y'] > fin_hyp['slope'] * data['x'] + fin_hyp['constant'] > outputs > # Add a plot showing points above and below the line > # ifelse is vectorized so it creates a vector with > # 16 (symbol for solid circle) if above the line and > # 1 (open circle) if below the line > sym <- ifelse(outputs, 16, 1) > plot(y~x, data, pch=sym) > abline(a=fin_hyp$constant, b=fin_hyp$slope) > > > David L. Carlson > Department of Anthropology > Texas A&M University > > -----Original Message----- > From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Duncan > Murdoch > Sent: Friday, November 13, 2015 1:16 PM > To: Ilgaz S <ilgaz.so...@gmail.com>; r-help@r-project.org > Subject: Re: [R] Suprising R behaviour > > On 13/11/2015 8:11 AM, Ilgaz S wrote: > > Hello everybody, I am new to R and I discovered something that suprise me > > and I have a question about it. > > Today I wanted to return a bit array which represents this: > > > > if( arbitrary point above the line) > > return TRUE > > else > > return FALSE > > > > First I tought I would use for loop and access every element of the data. > > Then I tend to use lapply function. > > > > At the end, I accidently done that without using any if/else statement. ( > > or for loop ) Here is the code: > > I can't read your code (you posted in HTML, don't do that), but it > sounds as though you have discovered vectorized operations. These are > central to good R programming, and are well described in the > Introduction to R manual. > > Duncan Murdoch > > > > data <- data.frame(x= c(1,2,3,1,1,1), y = c(1,2,3,4,6,7))fin_hyp <- > > list(slope=2,constant=1)outputs <- data['y'] > fin_hyp['slope'] * > > data['x'] +fin_hyp['constant']outputs > > > > What is R doing here? It is using loop somewhere inside? Is this code > > more efficient than other methods I mentioned? > > > > Thank you, I.S. > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > > https://stat.ethz.ch/mailman/listinfo/r-help > > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > > and provide commented, minimal, self-contained, reproducible code. > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
