[R] how to combine logic test on vectors in R?

[Luigi Marongiu]

Thank you! I have been thinking of using length but it would make the
test more complex. I did not know about all() but it looks like the
tool for the job. Cheers

On Thu, Sep 30, 2021 at 6:24 PM Eric Berger <ericjberger using gmail.com> wrote:
>
> Alternatively you can modify the test as follows:
>
> length(unique(df_b$q)) == 1
>
>
>
> On Thu, Sep 30, 2021 at 7:22 PM Bert Gunter <bgunter.4567 using gmail.com> wrote:
>>
>> I haven't followed this thread closely, but to your question I think
>> maybe this is what you want"
>>
>> > z <- c("","")
>> > all(z == "")
>> [1] TRUE
>> > z <- c("a","")
>> > all(z == "")
>> [1] FALSE
>>
>> If this isn't it, just ignore without reply.
>>
>> Bert Gunter
>>
>> "The trouble with having an open mind is that people keep coming along
>> and sticking things into it."
>> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>>
>> On Thu, Sep 30, 2021 at 8:51 AM Luigi Marongiu <marongiu.luigi using gmail.com> wrote:
>> >
>> > Yes, but the && should work within `unique(df_b$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.goslee using 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.luigi using 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 using 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
>> >
>> >
>> >
>> > --
>> > Best regards,
>> > Luigi
>> >
>> > ______________________________________________
>> > R-help using 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 using 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.



-- 
Best regards,
Luigi