Rescales a value column so the chosen base year equals to (100 by default),
per country – the standard way to compare trajectories that start at very
different levels.
Examples
df <- data.frame(iso3c = "USA", year = 2000:2002, gdp = c(50, 55, 60))
index_to(df, gdp, base_year = 2000)
#> # A tibble: 3 × 4
#> iso3c year gdp gdp_index
#> <chr> <int> <dbl> <dbl>
#> 1 USA 2000 50 100
#> 2 USA 2001 55 110
#> 3 USA 2002 60 120
