[R] Help with study guide for R exam
343GS
robbiesqp at gmail.com
Thu Dec 8 20:34:49 CET 2011
Hi there. I have a final exam coming up in a class that is heavily based in
the R programming language. The teacher has provided to us a few questions
to study in preparation for the exam. I was looking to see if anyone could
help answer any or all of these questions. Your help is extremely
appreciated! Thank you! - Spark
1. Write the first 6 lines of a hypothetical external data file named infile
that will be completely read by the following R command:
mydata <- read.table(“infile”, skip=3, header=FALSE, sep=’,’,
colClasses=c(‘character’, rep(‘numeric’, 3) ) )
2. Describe and fix the error in the following R command.
if(mydata[,2]=2) {mydata[,2]=mydata[,2]*2}
3. Write 1 or more R statements that will calculate the mean, sum, and
standard deviation of the numeric columns of mydata described in question
#1.
4. What type of data structure is produced by the R command in question #1?
5. What type of data structure is returned by the which statement in the
following R command?
myresult <- mydata[which(mydata[,1]>
6. Be able to fully describe the characteristcs and advantages of the
following data structures:
vector, dataframe, matrix, list
7. Be able to describe the following data types:
character, numeric, logical, date, factor
8. Describe several advantages and disadvantages to the R open-source
development process (ie. of the R system development)
9. What is an R package?
10. What makes R different from a language like Fortran or C?
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