geom_bar: color gradient and cross hatches (using gridSVG), transparency issue

Question

Using the awesome ggplot package, I want a barplot where the fill aesthetic is mapped to a continous variable, actually qvalues and on top of it a text

Answer 1

I am answering my own question, as there is a way to fill a specific color to the pattern thank to this link. On the first bar, for category "A", it could look like this:

replacing the pat1 pattern by the following code:

pat1 <- pattern(gTree(children=gList(
                      rectGrob(gp=gpar(col=NA, fill=cols[4])),
                      linesGrob(gp=gpar(col="black", lwd = 5)))),
                      width = unit(5, "mm"), height = unit(5, "mm"),
                      dev.width = 1, dev.height = 1)

For geom_bar with few colours, it would work but for my issue where the fill colour is mapped to a heatmap scale, it is going to be tedious.