Rebase a series to an index (base year = 100)

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.

Usage

index_to(data, value, base_year, to = 100, suffix = "_index")

Arguments

data

A panel with iso3c and year.

value

The value column (unquoted).

base_year

The year set equal to to. A country that has no row for this year indexes to NA rather than stopping the call, because the rebasing is per country and a partial answer is still a real one. That also means a base_year no row anywhere carries – including any non-integer value, which no year can equal – yields an all-NA column rather than an error. deflate(), whose rebasing is global, refuses such a year instead; check with base_year %in% data$year if you need that.

to

The index value the base year maps to (default 100).

suffix

Suffix for the new column (default "_index").

Value

data with an index column added. The column is NA for any country whose series does not cover base_year (see the note there).

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

# A base year the data does not have gives NA, not an error:
index_to(df, gdp, base_year = 1999)
#> Warning: 1 country has no usable 1999 value; gdp_index is all NA for it:
#> • "USA"
#> ℹ Choose a `base_year` the panel covers, or drop those countries first.
#> # A tibble: 3 × 4
#>   iso3c  year   gdp gdp_index
#>   <chr> <int> <dbl>     <dbl>
#> 1 USA    2000    50        NA
#> 2 USA    2001    55        NA
#> 3 USA    2002    60        NA