[R] If find x, then y, else do nothing

[Joshua Wiley]

On Fri, Aug 5, 2011 at 2:34 PM, Edward Patzelt <patze003 at umn.edu> wrote:
>
> The problem is that we were using a task where some subjects responded with "1 & 2" and some responded with "2 & 4".  So there is overlap for 2 because it means stimulus 1 for subject 1 and it means stimulus 2 for subject 2.
>
> subject
>
> subject_1
>
> 1
>
> subject_1
>
> 1
>
> subject_1
>
> 1
>
> subject_1
>
> 2
>
> subject_1
>
> 2
>
> subject_2
>
> 4
>
> subject_2
>
> 2
>
> subject_2
>
> 2
>
> subject_2
>
> 4
>
> subject_2
>
> 2
>
> subject_2
>
> 2
>
> subject_2
>
> 2
>
> subject_2
>
> 4

FYI providing data in the format above (this list is plain text) makes
the job of those trying to help substantially harder.  You can use
dput().  For example, if I wanted to share the first 10 rows of the
built in mtcars data set, I would just copy and paste the output from
running:

dput(mtcars[1:10, ])

Anyway, here you go, this should be directly executable as long as you
have installed the 'car' package.

## your data in a form easily copied and pasted into the console
## created using dput() (highly recommended for future posts)
dat <- structure(list(subject = c("subject_1", "subject_1", "subject_1",
"subject_1", "subject_1", "subject_2", "subject_2", "subject_2",
"subject_2", "subject_2", "subject_2", "subject_2", "subject_2"
), val = c(1, 1, 1, 2, 2, 4, 2, 2, 4, 2, 2, 2, 4)), .Names = c("subject",
"val"), row.names = c(NA, -13L), class = "data.frame")

## load the required package for recoding
## though it is overkill for only two levels
require(car)

## define a function to do the recoding
foo <- function(x) {
  if (any(grepl(4, x))) {
    x <- recode(x, "2 = 1; 4 = 2")
  }
  return(x)
}

## do it
dat$altval <- with(dat, ave(val, subject, FUN = foo))

Cheers,

Josh


>
> On Fri, Aug 5, 2011 at 4:25 PM, Joshua Wiley <jwiley.psych at gmail.com> wrote:
>>
>> Hi Edward,
>>
>> You can try something like:
>>
>> u.ppl <- unique(init.dat1$grid)
>> l.ppl <- ifelse(grepl(4, init.dat1$Slide1_RESP), 2,
>>                init.dat1$Slide1_RESP)
>>
>> Note that this is not exact as you have not provided a reproducible
>> example.  I am not exactly sure how you are  putting 1 for 2 and 2 for
>> 4, if the value is equal to 4, but presumably it is clearer with data.
>>  In any event, look at ?ifelse it is something like a vectorized if
>> statement and is, I believe, preferable to your use of a for loop.  I
>> can probably give you a runnable solution if you can give the first
>> few rows of the relevant data.
>>
>> Cheers,
>>
>> Josh
>>
>> On Fri, Aug 5, 2011 at 2:15 PM, Edward Patzelt <patze003 at umn.edu> wrote:
>> > I want to write code that says "If you find an element equal to 4 in this
>> > vector for each person in the data set tested separately, then put in 1 for
>> > 2 and 2 for 4, else leave the variable as is"
>> >
>> >  u.ppl <- (unique(init.dat1$grid))
>> >      l.ppl <- length(u.ppl)
>> >        for (i in 1:l.ppl)
>> >        {
>> >          if (grep("4",init.dat1$Slide1_RESP)) {2 == 1, 4 == 2}; else
>> > init.dat1$Slide1_RESP
>> >
>> >        }
>> >
>> > --
>> > Edward H. Patzelt
>> > Research Assistant – TRiCAM Lab
>> > University of Minnesota – Psychology/Psychiatry
>> > VA Medical Center
>> > Office: S355 Elliot Hall - Twin Cities Campus
>> > Phone: 612-626-0072  Email: patze003 at umn.edu
>> >
>> > Please consider the environment before printing this email
>> > www.psych.umn.edu/research/tricam
>> >
>> >        [[alternative HTML version deleted]]
>> >
>> >
>> > ______________________________________________
>> > R-help at 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
>> Programmer Analyst II, ATS Statistical Consulting Group
>> University of California, Los Angeles
>> https://joshuawiley.com/
>
>
>
> --
> Edward H. Patzelt
> Research Assistant – TRiCAM Lab
> University of Minnesota – Psychology/Psychiatry
> VA Medical Center
> Office: S355 Elliot Hall - Twin Cities Campus
> Phone: 612-626-0072  Email: patze003 at umn.edu
>
> Please consider the environment before printing this email
> www.psych.umn.edu/research/tricam



--
Joshua Wiley
Ph.D. Student, Health Psychology
Programmer Analyst II, ATS Statistical Consulting Group
University of California, Los Angeles
https://joshuawiley.com/