Usage
midpoint(x, ...)
## S3 method for class 'default':
midpoint(x, ...)
## S3 method for class 'numeric':
midpoint(x, ...)
## S3 method for class 'waveband':
midpoint(x, ...)
## S3 method for class 'generic_spct':
midpoint(x, ...)
## S3 method for class 'generic_mspct':
midpoint(x, ..., idx = !is.null(names(x)))