Week 1 Quiz | Quizerry

Week 1 Quiz >> Getting and Cleaning Data

and load the data into R. The code book, describing the variable names is here:

How many properties are worth $1,000,000 or more?

1 point

2076

164

Tidy data has no missing values.

Tidy data has one variable per column.

Each variable in a tidy data set has been transformed to be interpretable.

Numeric values in tidy data can not represent categories.

Read rows 18-23 and columns 7-15 into R and assign the result to a variable called:

What is the value of:

1 point

154339

33544718

36534720

181

127

100

130

using the fread() command load the data into an R object

The following are ways to calculate the average value of the variable

broken down by sex. Using the data.table package, which will deliver the fastest user time?

1 point

mean(DT$pwgtp15,by=DT$SEX)

sapply(split(DT$pwgtp15,DT$SEX),mean)

mean(DT[DT$SEX==1,]$pwgtp15); mean(DT[DT$SEX==2,]$pwgtp15)

DT[,mean(pwgtp15),by=SEX]

rowMeans(DT)[DT$SEX==1]; rowMeans(DT)[DT$SEX==2]

tapply(DT$pwgtp15,DT$SEX,mean)

Week 1 Quiz >> Getting and Cleaning Data