melt_spectra: Melts the spectra data of a Spectra object and returns it as wide format.

Description

This function is very useful when wanting to plot spectra using the lattice or ggplot2 packages

Usage

melt_spectra(obj, attr=NULL, ...)
# S4 method for SpectraDataFrame
melt_spectra(obj, attr = NULL, ...)

Arguments

obj

an object of class "Spectra" or inheriting from this class

attr

vector of id variables against which the spectra will be melted (see melt)

...

further arguments passed to or from other methods

Methods

x=Spectra

melt_spectra(obj, ...)

rll obj A Spectra object ... Ignored

x=SpectraDataFrame

melt_spectra(obj, attr=NULL, ...)

rll obj A SpectraDataFrame object attr Character, the name of an attribute in the object data to split the spectra against. ... Ignored

References

Hadley Wickham (2011). The Split-Apply-Combine Strategy for Data Analysis. Journal of Statistical Software, 40(1), 1-29. URL http://www.jstatsoft.org/v40/i01/.

Examples

Run this code

# NOT RUN {
# Loading example data
data(australia)
spectra(australia) <- sr_no ~ ... ~ 350:2500

# Simple melt
r <- melt_spectra(australia)
head(r)

# }
# NOT RUN {
# Melt against some factor (or continuous data), and plot
# using ggplot2

# Create some factor
australia$fact <- sample(
  LETTERS[1:3], 
  size = nrow(australia), 
  replace = TRUE
)
r <- melt_spectra(australia, attr = 'fact')

# Create plot
library(ggplot2)
p <- ggplot(r) + 
  geom_line(aes(x=wl, y=nir, group=id, colour=fact)) + 
  theme_bw()
print(p)
# }
# NOT RUN {
# }