DESCRIPTION

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QUESTION

(20 pts)  Fill in the blank with a term from our course:  Say we are
interested in finding the most well-received movie, and write code to
determine which movie has the highest average rating.  This might be
misleading, due to the phenomenon of _____________________.

QUESTION -ext .R -run 'Rscript omsi_answer2.R'

(20 pts)  We discussed another method of scaling besides subtracting the
mean and dividing by the standard deviation, which is mapping to the
interval [0,1].  Write the function map01(x), which transforms the
vector x in this manner.  It will return an S3 object of class 'm01',
with components newx, the transformed vector; m, the minimum value of
the original x; and M, the maximum value of the original x.

map01 <- function(x) {

}

newNile <- map01(Nile)  # Nile is a built-in dataset in R
print(sd(newNile$newx))  # about 0.185

QUESTION

(20 pts) In Question 2 above, why is it necessary to record minx and maxx,
i.e. why not just return newx?

QUESTION -ext .R -run 'Rscript omsi_answer4.R'

() Write a function lp(x,p) will find the l_p norm of a vector x.  Here
p can take on any real value between 1 and Inf, inclusive (Inf is the R
symbol for infinity).

lp <- function(x,p) {

}

# LakeHuron is another built-in dataset
print(lp(LakeHuron,2))  # about 5731.9
print(lp(LakeHuron,1))  # 56742.4
print(lp(LakeHuron,Inf))  # 581.86

QUESTION

(20 pts) In Homework II, it is suggested that you use only the first two
digits of ZIP code.  Explain the motivation for that, and why the first
two digits may still be useful.