One of the problems in my assignment for class is the following:

# Calculate a so-called "trimmed mean" of column 9 of x_mat by trimming off 5 percent of the values from each end of x. Please do not store the result in an object.

I have to be making this harder than it actually is. Here is what I came up with:

mean(x_mat[, 9], trim = 0.1)