README.md

In GeoIndexR: Computation of Spectral and Geospatial Indices from Multispectral Raster Data

GeoIndexR

GeoIndexR: A flexible, fast, and extensible R framework for computing spectral and geospatial indices from raster data, combining ready-to-use standard indices with a secure custom formula engine.

Built natively on terra, GeoIndexR enables researchers, remote sensing scientists, and GIS professionals to calculate standard indices or define their own custom formulas seamlessly.

Key Features

• 🛰️ Unified SpatRaster & File Path API: Pass terra::SpatRaster objects or direct file paths ("image.tif").
• 🧩 Custom Formula Engine (geo_index_custom()): Define arbitrary mathematical expressions ("(nir - red) / (nir + red)") with custom parameters and secure AST execution.
• 🎯 Intelligent Band Resolution: Map bands by index (c(red = 3, nir = 4)), layer name (c(red = "B4", nir = "B8")), or sensor preset (sentinel2, landsat8, landsat9).
• ⚖️ Reflectance & Scale Factor Management: Built-in support for scale_factor = 10000 to convert integer Digital Numbers (DN) into physical surface reflectance $[0, 1]$.
• 🛡️ Zero-Division & Singularity Safety: Automatic near-zero denominator tolerance and conversion of non-finite values to NA without arbitrary clamping.
• 📚 Rich Metadata Registry (index_registry()): Comprehensive catalog of indices with descriptions, purposes, interpretations, limitations, and literature citations.
• 📊 Descriptive Statistics & Plotting: Detailed summaries with percentiles (index_summary()) and thematic color ramps (plot_index()).

Supported Standard Indices

| Index | Category | Required Bands | Formula | Reference | | :--- | :--- | :--- | :--- | :--- | | NDVI | Vegetation | nir, red | $(NIR - RED) / (NIR + RED)$ | Rouse et al. (1974) | | SAVI | Vegetation | nir, red | $((NIR - RED) / (NIR + RED + L)) \times (1 + L)$ | Huete (1988) | | EVI | Vegetation | nir, red, blue | $G \times (NIR - RED) / (NIR + C_1 RED - C_2 BLUE + L)$ | Liu & Huete (1995) | | MSAVI | Vegetation | nir, red | $(2 NIR + 1 - \sqrt{(2 NIR + 1)^2 - 8(NIR - RED)}) / 2$ | Qi et al. (1994) | | OSAVI | Vegetation | nir, red | $((NIR - RED) / (NIR + RED + \theta)) \times (1 + \theta)$ | Rondeaux et al. (1996) | | ARVI | Vegetation | nir, red, blue | $(NIR - RB) / (NIR + RB)$ | Kaufman & Tanre (1992) | | GNDVI | Vegetation | nir, green | $(NIR - GREEN) / (NIR + GREEN)$ | Gitelson et al. (1996) | | NDWI | Water | green, nir | $(GREEN - NIR) / (GREEN + NIR)$ | McFeeters (1996) | | MNDWI | Water | green, swir1 | $(GREEN - SWIR1) / (GREEN + SWIR1)$ | Xu (2006) | | AWEI | Water | green, nir, swir1, swir2 | $4(GREEN - SWIR1) - (0.25 NIR + 2.75 SWIR2)$ | Feyisa et al. (2014) | | NDBI | Urban | swir1, nir | $(SWIR1 - NIR) / (SWIR1 + NIR)$ | Zha et al. (2003) | | IBI | Urban | swir1, nir, red, green | $(NDBI - (SAVI + MNDWI)/2) / (NDBI + (SAVI + MNDWI)/2)$ | Xu (2007) | | NDMI | Moisture | nir, swir1 | $(NIR - SWIR1) / (NIR + SWIR1)$ | Gao (1996) | | MSI | Moisture | swir1, nir | $SWIR1 / NIR$ | Rock et al. (1986) | | BSI | Soil | swir1, red, nir, blue | $((SWIR1 + RED) - (NIR + BLUE)) / ((SWIR1 + RED) + (NIR + BLUE))$ | Rikimaru et al. (2002) | | NDSI | Snow | green, swir1 | $(GREEN - SWIR1) / (GREEN + SWIR1)$ | Hall et al. (1995) |

Installation

Install the latest version from GitHub:

# install.packages("devtools")
devtools::install_github("sowsalim01/GeoIndexR")

Quick Start

library(GeoIndexR)
library(terra)

# 1. Load raster image (or provide filepath: "image.tif")
img <- get_example_data()

# 2. Compute a standard index
ndvi <- geo_index(img, "NDVI", bands = c(red = "red", nir = "nir"))

# 3. Compute a scale-sensitive index with scale_factor (e.g. for Sentinel-2 DN)
evi <- geo_index(
  img,
  "EVI",
  bands = c(blue = "blue", red = "red", nir = "nir"),
  scale_factor = 1 # or 10000 for raw integer DN
)

# 4. Compute a custom user formula
custom <- geo_index_custom(
  img,
  formula = "(nir - swir1) / (nir + swir1)",
  bands = c(nir = "nir", swir1 = "swir1"),
  name = "CustomMoistureIndex"
)

# 5. Summarize statistics with percentiles
index_summary(ndvi)

# 6. Plot the index
plot_index(ndvi, "NDVI")

# 7. Save output to GeoTIFF
writeRaster(ndvi, "NDVI_result.tif", overwrite = TRUE)

License

MIT © Mamadou Sow

GeoIndexR documentation built on Oct. 10, 2026, 5:08 p.m.