> Hi, > > For a good discussion of the link between colour and spectra I would > suggest, > > http://www.fourmilab.ch/documents/specrend/ > > which provides an open-source C code to perform the conversion you ask > for. I asked for some advice on how to wrap a R function around this > code last week but sadly I didn't get anywhere. Do let me know if you > succeed. (alternatively, one could port the implementation in pure R > as the code is not too complicated or computationally demanding). > > Hope this helps, > > baptiste >
I have visited the site before I posted my question. I don't know what's the relationship between black body spectra and specific wavelength. And frankly, I don't understand C. I have translate a Fortran code (http://www.isc.tamu.edu/~astro/color/spectra.html) to R as given below, however, I don't know how to modify it and make it could accept a vector, e.g., 380:780, as input. And when plot a line, how to color the line using different color? Thanks in advance! Jinsong wl2rgb <- function(wl, gamma) { if (missing(gamma)) gamma <- 1 if (wl >= 380 & wl <= 440) { r <- -1 * (wl - 440) / (440 - 380) g <- 0 b <- 1 } if (wl >= 440 & wl <= 490 ) { r <- 0 g <- (wl - 440) / (490 - 440) b <- 1 } if (wl >= 490 & wl <= 510) { r <- 0 g <- 1 b <- -1 * (wl - 510) / (510 - 490) } if (wl >= 510 & wl <= 580) { r <- (wl - 510) / (580 - 510) g <- 1 b <- 0 } if (wl >= 580 & wl <= 645) { r <- 1 g <- -1 * (wl - 645) / (645 - 580) b <- 0 } if (wl >= 645 & wl <= 780) { r <- 1 g <- 0 b <- 0 } s <- 1 if (wl > 700) { s <- .3 + .7 * (780 - wl) / (780 - 700) } if ( wl < 420) { s <- .3 + .7 * (wl - 380) / (420 - 380) } r <- as.integer(255 * (s * r)^gamma) g <- as.integer(255 * (s * g)^gamma) b <- as.integer(255 * (s * b)^gamma) return(rgb(r, g, b, maxColorValue = 255)) } ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
