# swcEcon 0.1.0

## First CRAN release

### New functions (16 exported)
* `calc_bcr()` -- Benefit-cost ratio with discounting, benefit lag, residual value.
* `calc_npv()` -- Net present value with annual cash-flow table.
* `calc_irr()` -- Internal rate of return via bisection (Brent 1973).
* `calc_pbp()` -- Simple and discounted payback period.
* `calc_mrr()` -- Marginal rate of return (CIMMYT 1988).
* `calc_mbcr()` -- Modified benefit-cost ratio (Gittinger 1982).
* `calc_soil_loss_cost()` -- USLE-based soil loss economic valuation.
* `calc_nutrient_cost()` -- NPK replacement cost from erosion.
* `calc_water_value()` -- Groundwater recharge and runoff harvesting value.
* `calc_irrigation_benefit()` -- Additional crop income from SWC-enabled irrigation.
* `calc_employment()` -- Employment generation ratio with MGNREGS norm check.
* `sensitivity_analysis()` -- One-at-a-time sensitivity analysis (8 scenarios).
* `calc_switching_value()` -- Switching value for cost and benefit.
* `monte_carlo_swc()` -- Stochastic BCR/NPV simulation (Pouliquen 1970).
* `run_swc_pipeline()` -- Full appraisal pipeline in one call.
* `generate_swc_report()` -- Self-contained HTML economic appraisal report.

### Datasets (6)
* `swc_benchmarks` -- Real: NABARD WDF Reports 2010-2022; PMKSY-WDC (GoI).
* `usle_india_soils` -- Real: NBSS and LUP Technical Bulletin 132 (ICAR).
* `rainfall_erosivity_india` -- Real: IMD + Bhattacharyya et al. (2010).
* `swc_cost_norms` -- Real: PMKSY-WDC Common Guidelines (GoI 2015).
* `watershed_projects` -- Hypothetical: set.seed(2025), 50 projects.
* `farmer_adoption` -- Hypothetical: set.seed(2025), 120 households.

### Technical notes
* All source files are pure ASCII -- CRAN portable.
* Dataset documentation uses NULL sentinel pattern for roxygen2 compatibility.
* Zero runtime dependencies beyond base R (stats, graphics, grDevices, utils).
* `markdown = FALSE` in DESCRIPTION -- plain Rd syntax throughout.
