Hi Joshua, Thanks for your advice.
> assign(x = "temp", value = 1:5 > 1) > using the assign function (not often recommended) to avoid any > confusion with the assignment operator, "<-". > temp [1] FALSE TRUE TRUE TRUE TRUE I got it. Thanks B.R. Stephen L ----- Original Message ---- From: Joshua Wiley <jwiley.ps...@gmail.com> To: Stephen Liu <sati...@yahoo.com> Cc: r-help@r-project.org Sent: Thu, November 4, 2010 2:46:15 PM Subject: Re: [R] Logical vectors On Wed, Nov 3, 2010 at 10:50 PM, Stephen Liu <sati...@yahoo.com> wrote: > Hi folks, > > Pls help me to understand follow; > > An Introduction to R > > 2.4 Logical vectors > http://cran.r-project.org/doc/manuals/R-intro.html#R-and-statistics > > 1) >> x > [1] 1 2 3 4 5 a vector, x, is defined with 5 elements, {1, 2, 3, 4, 5} >> temp <- x != 1 perform the logical test that x does not equal 1 returning either TRUE or FALSE. 1 = 1 so TRUE, 2 != 1 so FALSE, etc. next we assign *the results* of the logical test to the vector 'temp' >> temp > [1] FALSE TRUE TRUE TRUE TRUE print the vector to screen >> > > > 2) >> x > [1] 1 2 3 4 5 note that x has not changed here, we assigned to temp, not to x. >> temp <- x > 1 now we assign the results of the logical test, x > 1 {1 = 1 so FALSE, 2 > 1 so TRUE, 3 > 1 so TRUE, 4 > 1 so TRUE, 5 > 1 so TRUE} we assign these results to a vector, 'temp'. This *new* assignment overwrites the old vector 'temp' >> temp > [1] FALSE TRUE TRUE TRUE TRUE print temp to screen, this is the results of our second logical test (x > 1). > > > Why NOT >> temp > [1] TRUE FALSE FALSE FALSE FALSE My best guess of where you got confused is that we assigned the results to 'temp', so 'x' remained unchanged {1, 2, 3, 4, 5}, or that you confused '<-' which is the assignment operator in R, to "less than negative..." *OR* "less than or equal". We could write this equivalently: > 1:5 > 1 [1] FALSE TRUE TRUE TRUE TRUE this was the logical test, whose results were assigned to the vector, "temp". > assign(x = "temp", value = 1:5 > 1) using the assign function (not often recommended) to avoid any confusion with the assignment operator, "<-". > temp [1] FALSE TRUE TRUE TRUE TRUE print to screen HTH, Josh > > ? > > > TIA > > B.R. > Stephen L > > > > ______________________________________________ > R-help@r-project.org mailing list > 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. -- Joshua Wiley Ph.D. Student, Health Psychology University of California, Los Angeles http://www.joshuawiley.com/ ______________________________________________ R-help@r-project.org mailing list 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.