R programming - creating a graph, with variable colors

I do not have much experience in R, and I wonder if they can help me in this situation.

I have the following matrix:

mat <- matrix(c(0,0.5,0.2,0.23,0.6,0,0,0.4,
         0.56,0.37,0,0.32,0.4,0.99,0.54,0.6,0,0.39), ncol=6, nrow=3)

dimnames(mat) = list( 
                  c("y1","y2","y3"),
                  c("day1","day2","day3","day4","day5","day6")
                    )

> mat
   day1 day2 day3 day4 day5 day6
y1  0.0 0.23 0.00 0.37 0.40 0.60
y2  0.5 0.60 0.40 0.00 0.99 0.00
y3  0.2 0.00 0.56 0.32 0.54 0.39
>

I want to know how can I get a graph where points would be marked based on the matrix.

The values are arbitrary in the interval [0,1]. It is possible to change the color of the generated points as a set of constraints?

Example:

(0,0.2] - Red
(0.2,0.4] - Green
(0.4,0.6] - Yellow
(0.6,0.9] - Blue
(0.9,1] - Black

I apologize if I have not explained myself well.

Thank you!

Solution

If you just want coloured points, something like this will do it:

palette(c("red","green","yellow","blue","black"))
plot.default(
  as.data.frame.table(t(mat))[1:2],
  col=findInterval(t(mat),c(0,0.2,0.4,0.6,0.9)),
  pch=19,
  axes=FALSE,ann=FALSE,
  panel.first=grid()
)
axis(2,at=1:length(rownames(mat)),labels=rownames(mat),lwd=0,lwd.ticks=1,las=1)
axis(1,at=1:length(colnames(mat)),labels=colnames(mat),lwd=0,lwd.ticks=1)
box()
palette("default")

Result:

enter image description here