R - 如何找到多列的前 10%？

Question

For school, we are trying to find the top 10% of colleges in temrs of PhD's, Grad.Rate, and Enrollment. We are using the ISLR's College dataframe.

I have tried using head() with order() to order them well, but I am not really sure if all three of these colleges need to be within the top ten percent of each category.

The actual question verbatim: 'Create a dataframe that just includes the colleges that are in the top 10% in terms of PhD's, Grad.Rate and Enrollment.'

Thank you so much.

Answer 1

First, create a vector indicating whether a college is in the top 10 or not for a specific variable:

College$PhD_top10 <- ifelse(College$PhD >= quantile(College$PhD, probs = 0.9), TRUE, FALSE)

Repeat this for as many variables as you need.

Then subset the data frame based on those variables:

College[College$PhD_top10, ] # Add & to string along other created variables.

Answer 2

Try using quantile function

quantile(x, probs = seq(0, 1, by= 0.1)) # decile