On Thu, 11 May 2006, Arnab mukherji wrote:
Hi R-users,
I had a minor issue while demonstating R that I can't explain. I am
hoping someone will have suggestions. The only difference is a call to
fix() in between that I made to ensure people were following me.
However, that seems to have altered the way R code got executed.
I was wondeirng if people have any insights.
You did not create a factor, and in the first version 'pass' is character.
edit.data.frame (as used by fix) did some coercion.
It would be better to do
dat$pass <- factor(rep("Fail", 10), levels=c("Fail", "Pass"))
dat[ ind, "pass"] <- "Fail"
dat[ !ind, "pass"] <- "Pass"
and also rather than fix(dat), do
invisible(edit(dat))
which does not save changes.
Arnab
# When it does work
x <-letters[1:10]
marks <-runif(10)*100
dat <- data.frame(Student.id = x, Grade = rep(1:5,2), Marks = marks)
ind <- dat$Marks < 50
dat[ ind, "pass"] <- "Fail"
dat[!ind, "pass"] <- "Pass"
dat
Student.id Grade Marks pass
1 a 1 81.91246 Fail
2 b 2 67.66341 Pass
3 c 3 4.05249 Pass
4 d 4 94.37248 Fail
5 e 5 50.83555 Pass
6 f 1 16.34850 Fail
7 g 2 43.68585 Pass
8 h 3 49.67190 Fail
9 i 4 74.41275 Fail
10 j 5 86.15475 Fail
# When it Doesnÿÿt Work
x <-letters[1:10]
marks <-runif(10)*100
dat <- data.frame(Student.id = x, Grade = rep(1:5,2), Marks = marks)
ind <- dat$Marks < 50
dat[ ind, "pass"] <- "Fail"
fix(dat)
dat[!ind, "pass"] <- "Pass"
Warning message:
invalid factor level, NAs generated in: "[<-.factor"(`*tmp*`, iseq, value = c("Pass",
"Pass", "Pass",
dat
Student.id Grade Marks pass
1 a 1 72.14612 <NA>
2 b 2 64.34044 <NA>
3 c 3 20.27918 Fail
4 d 4 39.01875 Fail
5 e 5 92.19682 <NA>
6 f 1 58.74779 <NA>
7 g 2 35.31430 Fail
8 h 3 18.64664 Fail
9 i 4 51.58880 <NA>
10 j 5 77.94396 <NA
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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