Dear list:
I have a data frame with student name, class he attended and marks for
subjects he attended.
Students took second exam if they performed badly in their first attempt. I
want to consider the test scores where they obtain highest median.
there are 6 classes. As a sample case, I will consider only classes A, B
and C.
For class A, Student Raj took first exam and he did not score well. He
re-took his exam and scored well. his median marks second time was high, and
thus I will consider
only marks he scored second time. Similarly, for class A ,kiran took one
class and I have no choice but to consider his marks in his only attempt.
Matt took class B and performed poorly. In his second attempt, he scored
well and thus I will consider his second attempt because his median his
high.
Since only one student took class C and took exam only once, I will consider
Ram's test scores for the class he took.
Name
Class
Trigno
Algebra
Calculus
Sci.Comp
CS
Raj
A
10
20
12
24
20
Raj
A
20
21
25
25
25
Kiran
A
20
24
24
23
24
Matt
B
12
10
13
9
9
Matt
B
20
24
23
22
24
Ram
C
25
25
25
25
25
Rhea
D
21
12
12
21
23
Jack
E
12
15
16
18
19
Smita
F
13
18
19
19
20
> rtest
Name Class Trigno Algebra Calculus Sci.Comp CS
1 Raj A 10 20 12 24 20
2 Raj A 20 21 25 25 25
3 Kiran A 20 24 24 23 24
4 Matt B 12 10 13 9 9
5 Matt B 20 24 23 22 24
6 Ram C 25 25 25 25 25
7 Rhea D 21 12 12 21 23
8 Jack E 12 15 16 18 19
9 Smita F 13 18 19 19 20
I want to write a small loop program that would give me back a data frame.
>tclass <- c('A','B','C')
> tclass
[1] "A" "B" "C"
> for(i in 1:length(tclass)){
+ k = rtest[rtest$Class==tclass[i],]
+ if(nrow(k)>1){
+ x <- k[,c(-1,-2)]
+ rownames(x) <- k[,1]
+ k2 = apply(x,1,median)
+ fin_dat <- c(rtest$Name==max(names(k2)),)}
+ else{
+ fin_dat <- c(k)
+ }
+ }
Error in `row.names<-.data.frame`(`*tmp*`, value = c(4L, 4L, 2L)) :
duplicate 'row.names' are not allowed
my code:
for(i in 1:length(tclass)){
k = rtest[rtest$Class==tclass[i],] # selecting all students who took that
class
if(nrow(k)>1){ # if there are many students
then...
x <- k[,c(-1,-2)] # take only their scores
and leave their name and class column
rownames(x) <- k[,1] # to choose row of scores for a student
with high median, I am making row names and since the student names are
duplicated.. I am having problem
k2 = apply(x,1,median) # obtain median
fin_dat <- c(rtest$Name==max(names(k2)),)} # get test scores line
from original data frame and write back to fin_dat object
else{ # if a student took only once his
exam
fin_dat <- c(k) # write his score to fin_dat
}
}
Could any one please help me here with my problem. Since Raj is duplicated,
I am having this error. If there is a better way of doing this, I
appreciate your help.
Thanks
Ad.
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