plot - Matrix diagram in r -

i create such diagram in r:

i have such matrix

 [1]   [2]   [3]   [4]   [5] .... [30]  [1] 0.5   0.75  1.5   0.25  2.5 .... 0.51  [1] 0.84  0.24  3.5   0.85  0.25.... 1.75  [1] 0.35  4.2   0.52  1.5   0.35.... 0.75 . . ....................................... . [30]0.84  1.24  0.55   1.5  0.85.... 2.75 

and want have diagram,

• if value less 1 ----> green circle
• if value between 1 , 2 ----> yellow circle
• more 2 ----> red circle

is there packages or method in r job? how can that?

to plot this, need 3 data points:

x, y, color 

thus, first step reshaping.
fortunately, matricies vector, dimension attribute, need create data.frame of x,y coordinates. expand.grid.

# create sample data.  mat <- matrix(round(runif(900-30, 0, 5),2), 30) 

create (x, y) data.frame.
notice y seq of rows , x seq of columns

dat <- expand.grid(y=seq(nrow(mat)), x=seq(ncol(mat)))  ## add in values matrix.  dat <- data.frame(dat, value=as.vector(mat))  ## create column appropriate colors based on value. dat$color <- cut( dat$value,                    breaks=c(-inf, 1, 2, inf),                    labels=c("green", "yellow", "red")                  )    ## plotting library(ggplot2) ggplot(data=dat, aes(x=x, y=y)) + geom_point(color=dat$color, size=7)