Cluster multiple time series using K-means

I have been recently confronted to the issue of finding similarities among time-series and though about using k-means to cluster them. To illustrate the method, I’ll be using data from the Penn World Tables, readily available in R (inside the {pwt9} package):

library(tidyverse)
library(lubridate)
library(pwt9)
library(brotools)

First, of all, let’s only …