No it shouldn't work. unique returns zero or more results so == with a constant will be a logical vector zero or more elements long, which is inappropriate for &&. Use the any function perhaps.
On September 30, 2021 8:51:02 AM PDT, Luigi Marongiu <marongiu.lu...@gmail.com> wrote: >Yes, but the && should work within `unique(df_b$q) == ""` because the >test should be: (IF THE DATAFRAME HAS ZERO ROW) OR (ALL THE ELEMENTS >OF $q ARE EMPTY) THEN (PRINT empty). >Can I collapse the TRUE FALSE of `unique(df_b$q) == ""`into a single FALSE? > >On Thu, Sep 30, 2021 at 4:28 PM Sarah Goslee <sarah.gos...@gmail.com> wrote: >> >> Hi, >> >> The OR operator you used is working as expected: || starts from the >> left and evaluates only enough of the options to determine the >> results. The first test is TRUE, so the result is TRUE. It sounds >> like you might actually want an AND operator, & or &&, which will only >> return TRUE if all elements are TRUE, >> >> More on logical operators: >> https://stat.ethz.ch/R-manual/R-devel/library/base/html/Logic.html >> >> Sarah >> >> On Thu, Sep 30, 2021 at 9:07 AM Luigi Marongiu <marongiu.lu...@gmail.com> >> wrote: >> > >> > Hello, >> > I have two data frames, each with three rows: >> > ``` >> > df_a <- data.frame(a = letters[1:3], b = LETTERS[1:3], q = c("", "", ""), >> > stringsAsFactors = FALSE) >> > df_b <- data.frame(a = letters[4:6], b = LETTERS[4:6], q = c("", "", >> > "1.5"), >> > stringsAsFactors = FALSE) >> > ``` >> > I need to test whether the dataframe has been selected and if there is >> > a value in the q column. I combined in the following test: >> > ``` >> > if (nrow(df_a) == 0 || unique(df_a$q) == "") { >> > print("empty") >> > } >> > if (nrow(df_b) == 0 || unique(df_b$q) == "") { >> > print("empty") >> > } >> > ``` >> > The test for df_a worked as expected: >> > ``` >> > > nrow(df_a) == 0 >> > [1] FALSE >> > > unique(df_a$q) == "" >> > [1] TRUE >> > > (nrow(df_a) == 0 || unique(df_a$q) == "") >> > [1] TRUE >> > > if (nrow(df_a) == 0 || unique(df_a$q) == "") { >> > + print("empty") >> > + } >> > [1] "empty" >> > ``` >> > but the one for df_b did not: >> > ``` >> > > nrow(df_b) == 0 >> > [1] FALSE >> > > unique(df_b$q) == "" >> > [1] TRUE FALSE >> > > (nrow(df_b) == 0 || unique(df_b$q) == "") >> > [1] TRUE >> > > unique(df_b$q) >> > [1] "" "1.5" >> > ``` >> > I say that it did not work because unique(df_b$q) IS NOT "", hence >> > `(nrow(df_b) == 0 || unique(df_b$q) == "")` should be FALSE, instead R >> > evaluated the first element of unique(df_b$q) == "", which is TRUE. >> > How can I properly implement a logic test on vectors? >> > Thank you >> > >> > ______________________________________________ >> > 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. >> >> >> >> -- >> Sarah Goslee (she/her) >> http://www.sarahgoslee.com > > > -- Sent from my phone. Please excuse my brevity. ______________________________________________ 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.
