Spectral Angle Mapper Classification

Classifies each pixel by computing the spectral angle to a set of reference endmember spectra and assigning the class with the smallest angle.

Usage

hs_sam(cube, endmembers, threshold = 0.1)

Arguments

cube

An hsi_cube object.

endmembers

Named matrix or data.frame. Rows = endmembers, cols = bands. Row names become class labels.

threshold

Numeric. Maximum angle (radians) for assignment. Pixels exceeding this are classified as "unclassified". Default 0.1.

Value

A list with class "hsi_classification":

class_map

Character matrix (rows x cols) of class labels.

angle_map

3D array of angles to each endmember.

endmembers

The endmember matrix used.

Examples

cube <- hs_example_cube()
# Define endmembers from specific pixels
em <- rbind(
  healthy = cube$data[5, 5, ],
  ischemic = cube$data[25, 5, ]
)
result <- hs_sam(cube, em, threshold = 0.5)
table(result$class_map)
#> 
#>  healthy ischemic 
#>      407      493