Dear Jinsong,When you enter these code lines at the R command prompt, the interpreter evaluates an expression when it's syntactically complete, which occurs before it sees the else clause. The interpreter can't read your mind and know that an else clause will be entered on the next line. When the code lines are in a function, the function body is enclosed in braces and so the interpreter sees the else clause.
As I believe was already pointed out, you can similarly use braces at the command prompt to signal incompleteness of an expression, as in
> {if (FALSE) print(1)
+ else print(2)}
[1] 2
I hope this helps,
John
--
John Fox, Professor Emeritus
McMaster University
Hamilton, Ontario, Canada
web: https://socialsciences.mcmaster.ca/jfox/
On 2022-10-21 8:06 a.m., Jinsong Zhao wrote:
Thanks a lot!I know the first and third way to correct the error. The second way seems make me know why the code is correct in the function stats::weighted.residuals.On 2022/10/21 17:36, Andrew Simmons wrote:The error comes from the expression not being wrapped with braces. You could change it toif (is.matrix(r)) { r[w != 0, , drop = FALSE] } else r[w != 0] or { if (is.matrix(r)) r[w != 0, , drop = FALSE] else r[w != 0] } or if (is.matrix(r)) r[w != 0, , drop = FALSE] else r[w != 0] On Fri., Oct. 21, 2022, 05:29 Jinsong Zhao, <jsz...@yeah.net> wrote: Hi there, The following code would cause R error: > w <- 1:5 > r <- 1:5 > if (is.matrix(r)) + r[w != 0, , drop = FALSE] > else r[w != 0] Error: unexpected 'else' in " else" However, the code: if (is.matrix(r)) r[w != 0, , drop = FALSE] else r[w != 0] is extracted from stats::weighted.residuals. My question is why the code in the function does not cause error? Best, Jinsong ______________________________________________ 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 <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-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland 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.
