fill_proxy_growth: Fill gaps using growth rates from proxy variables

Description

Fills missing values using growth rates from a proxy variable (reference series). Supports regional aggregations, weighting, and linear interpolation for small gaps.

Usage

fill_proxy_growth(
  data,
  value_col,
  proxy_col,
  time_col = year,
  .by = NULL,
  max_gap = Inf,
  max_gap_linear = 3,
  fill_scope = NULL,
  value_smooth_window = NULL,
  proxy_smooth_window = 1,
  output_format = "clean",
  verbose = TRUE
)

Value

A data frame with filled values. If output_format = "clean", returns original columns with updated value_col and added source column. If "detailed", includes all intermediate columns.

Arguments

data

A data frame containing time series data.

value_col

The column containing values to fill.

proxy_col

Character or vector. Proxy variable(s) for calculating growth rates. Supports multiple syntax formats:

Simple numeric proxy (e.g., "population"): Auto-detects numeric columns and uses them as proxy variable. Inherits the .by parameter to compute proxy values per group.
Simple categorical proxy (e.g., "region"): Auto-detects categorical columns and interprets as value_col:region. Aggregates value_col by the specified groups.
Advanced syntax (e.g., "gdp:region"): Format is "variable:group1+group2". Aggregates variable by specified groups.
Hierarchical fallback (e.g., c("population", "gdp:region")): Tries first proxy, falls back to second if first fails.
Weighted aggregation (e.g., "gdp[population]"): Weight variable by specified column during aggregation.

time_col

The column containing time values. Default: year.

.by

A character vector with the grouping variables (optional).

max_gap

Numeric. Maximum gap size to fill using growth method. Default: Inf.

max_gap_linear

Numeric. Maximum gap size for linear interpolation fallback. Default: 3.

fill_scope

Quosure. Filter expression to limit filling scope. Default: NULL.

value_smooth_window

Integer. Window size for a centered moving average applied to the value column before gap-filling. Useful for variables with high inter-annual variability. If NULL (default), no smoothing is applied.

proxy_smooth_window

Integer. Window size for moving average smoothing of proxy reference values before computing growth rates. Default: 1.

output_format

Character. Output format: "clean" or "detailed". Default: "clean".

verbose

Logical. Print progress messages. Default: TRUE.

Details

Combined Growth Sequence (Hierarchical Interpolation):

When using multiple proxies with hierarchical fallback, the function implements an intelligent combined growth sequence strategy:

Better proxies (earlier in hierarchy) are tried first for each gap.
If a better proxy has partial coverage within a gap, those growth rates are used for the covered positions.
Fallback proxies fill only the remaining positions where better proxies are not available.
Values filled by better proxies are protected from being overwritten.

Examples

Run this code

# Fill GDP using population as proxy
data <- tibble::tibble(
  country = rep("ESP", 4),
  year = 2010:2013,
  gdp = c(1000, NA, NA, 1200),
  population = c(46, 46.5, 47, 47.5)
)

fill_proxy_growth(
  data,
  value_col = gdp,
  proxy_col = "population",
  .by = "country"
)