IdentifyNoise: Identify noise in hyperspectral reflectance data.

In HDR: Processing of hyperspectral reflectance data

Description

This function plots average, min and max reflectance and lets the user iteratively identify spectral regions with low SN ratio.

Usage

IdentifyNoise(x, waves)

Arguments

x	a dataframe containing reflectance data in n= ncol(x) bands, for m= nrow(x) samples.
waves	a vector containing the wavelengths of each spectral band

Details

colnames(x) should contain the wavelength of each spectral band, in the form: colnames(x)= paste("X", wavelength, sep= "")

Value

badwl: a vector containing the wavelength of each spectral band that was identified with low SN ratio

Note

Written for spectral processing library of Laboratory of Geo Information and Remote Sensing, Wageningen University

Author(s)

Hans D Roelofsen

References

hdroelofsen.nl

Examples

##---- Should be DIRECTLY executable !! ----
##-- ==>  Define data, use random,
##--  or do  help(data=index)  for the standard data sets.

## The function is currently defined as
function (x, waves) 
{
    setwd("D:/dropbox/A_Werk/F_Non-project/AlgemeenWUR/SpecRScripts/SampleData/")
    dat <- read.table("SampleHySpec.ASC", header = T, sep = ";")
    wavelengths <- dget("SampleWavelengths.ASC")
    PlotRefl <- function(x, waves) {
        if (length(waves) != ncol(x)) {
            stop("nbands of x and wavelenghs do not match")
        }
        graphics.off()
        x11()
        par(tck = 0.005)
        plot(waves, apply(x, 2, mean), type = "l", ylim = c(0, 
            1), axes = F, xlim = c(min(waves), max(waves)), xlab = NA, 
            ylab = NA, xaxs = "i", yaxs = "i")
        xaxat <- seq(min(waves[waves%%50 == 0]), max(waves[waves%%50 == 
            0]), by = 50)
        abline(v = xaxat, col = "lightgray", lty = "dotted")
        xaxlab <- xaxat
        xaxlab[xaxlab%%100 != 0] <- NA
        axis(1, at = xaxat, labels = xaxlab, cex.axis = 0.75, 
            las = 2, pos = 0)
        axis(2, cex.axis = 0.75, pos = min(waves), las = 2)
        par(tck = 0.02)
        axis(1, at = xaxlab, pos = 0, labels = NA)
        title(xlab = "Wavelength", ylab = "Reflection")
        lines(waves, apply(x, 2, min), col = "darkgray")
        lines(waves, apply(x, 2, max), col = "darkgray")
        box()
        legend("topleft", c("mean", "min- max"), col = c("black", 
            "darkgray"), bty = "n", cex = 0.75, lty = rep("solid", 
            2))
    }
    good <- "n"
    while (good == "n") {
        PlotRefl(x = dat, waves = wavelengths)
        th <- as.numeric(unlist(strsplit(readline("Enter wavelength ranges to be removed, seperated by a comma: "), 
            ",")))
        if (length(th)%%2 != 0) {
            stop("number of range indicators should be multiple of 2")
        }
        bad.wl <- numeric()
        for (i in seq(1, length(th), by = 2)) {
            rect(th[i], 0, th[i + 1], 1, col = "#0000ff22", border = NA)
            bad.wl <- append(bad.wl, c(seq(th[i], th[i + 1])))
        }
        good <- readline("Is this an acceptable range of wavelengths to filter? y/n ")
    }
  }

HDR documentation built on May 2, 2019, 6:47 p.m.