[R] computation on a table
Claus Atzenbeck
claus.atzenbeck at freenet.de
Sat Nov 12 23:41:33 CET 2005
Hello,
I have a table (1) of the form
q1 q3 q4 q8 q9
A 5 2 0 1 3
B 2 0 2 4 4
I have another table (2):
q1 q2 q3 q4 q5 q6 q7 q8 q9
C 10 7 4 2 6 9 3 1 2
I would like to divide the numbers in table (1) by the number of the
appropriate column in table (2):
q1 q3 q4 q8 q9
A 5/10 2/4 0/2 1/1 3/2
B 2/10 0/4 2/2 4/1 4/2
The result would look lie this:
q1 q3 q4 q8 q9
A 0.5 0.5 0 1 1.5
B 0.2 0 1 4 2
BACKGROUND: I have a data frame with measured times for answering
questions. I want to know how many PERCENT of the answers are wrong,
caused by reason A or B.
This gives me the subset of false answers. The table looks like table (1):
fail <- subset(questions, type=="wrong")
fail$qid <- factor(fail$qid)
failtab <- table(fail$failtype, fail$qid)
The following gives me information about how often a specific question
was asked. This is similar to table (2) above.
count <- table(questions$failtype, questions$qid)
count <- colSums(count)
One solution would be to delete the line that calls factor(...) on the
subset and calculate failtab/count. However, then I have the problem
that I have to get rid of all columns of the table that have '0' in all
rows.
Thanks for any hint.
Claus
More information about the R-help
mailing list