From two colors to 01 sequences

Depending on the nature of your pdf file, it may be possible to use
the grImport package. I've never used it before, but a quick test
seems promising,

?# create a test picture
colorStrip <-
function (colors, draw = T)
{
? ? x <- seq(0, 1 - 1/ncol(colors), length = ncol(colors))
? ? y <- rep(0.5, length(colors))
? ? my.grob <- grid.rect(x = unit(x, "npc"), y = unit(y, "npc"),
? ? ? ? width = unit(1/ncol(colors), "npc"), height = unit(1,
? ? ? ? ? ? "npc"), just = "left", hjust = NULL, vjust = NULL,
? ? ? ? default.units = "npc", name = NULL, gp = gpar(fill =
rgb(colors[1,
? ? ? ? ? ? ], colors[2, ], colors[3, ]), col = rgb(colors[1,
? ? ? ? ? ? ], colors[2, ], colors[3, ])), draw = draw, vp = NULL)
? ? my.grob
}


colors <- rbind(c(1, 0, 1), c(0, 1, 0), c(0, 0, 0))

pdf("testRGB.pdf")
colorStrip(colors)
dev.off()


# import the pdf file into R
library(grImport)
PostScriptTrace("testRGB.pdf")

test <- readLines("testRGB.pdf.xml")

testRead <- readPicture("testRGB.pdf.xml")

str(testRead)
grid.picture(testRead) # somehow I've lost the fill color in the
process?!

grep("<rgb.+", test, value=T) # this should allow you to find the
sequence of red and green rectangles

HTH,

baptiste




On 12 May 2009, at 13:38, Zeljko Vrba wrote:

I have got several pdf files with rows of colored rectangles: red
rectangles should be read as 0; green rectangles as 1. No other color
exists. Is there some way to have R reading the colored rectangles to
a matrix or data frame converting the color of the rectangles to
sequences of 01?