R - filled.contour plot

filled.contour

• if you have a matrix with nxm dimensions and every entry represents a value of interest and the indices of the entry describe the position, then you can use filled.contour() to visualize the matrix
• first we create a simple matrix to demonstrate how it works:

x <- y <- 1:10 # create two vectors with the integers from 1 to 10
z <- outer(x,y) # create a matrix as the outer product of the two vectors
z # show the matrix

      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
 [1,]    1    2    3    4    5    6    7    8    9    10
 [2,]    2    4    6    8   10   12   14   16   18    20
 [3,]    3    6    9   12   15   18   21   24   27    30
 [4,]    4    8   12   16   20   24   28   32   36    40
 [5,]    5   10   15   20   25   30   35   40   45    50
 [6,]    6   12   18   24   30   36   42   48   54    60
 [7,]    7   14   21   28   35   42   49   56   63    70
 [8,]    8   16   24   32   40   48   56   64   72    80
 [9,]    9   18   27   36   45   54   63   72   81    90
[10,]   10   20   30   40   50   60   70   80   90   100

• now let us plot the matrix:

filled.contour(z)

• the matrix is mapped to a 1x1 square: the entry with the indices (1,1) and the value 1 to the point with the coordinates (0,0) and the entry with the indices (10,10) and the value (100) to the points with the coordinates (1,1); if you want to change the axes you can add a x and a y argument to the plot;so let's use the vectors x and y from above (with the entries 1 to 10) and also change to colors
• filled.contour() uses the cm palette as default (cyan for low, magenta for heigh values);

filled.contour(x=x,y=y,z, col=heat.colors(20))

• more palettes you find here

And a last example

my.seq <- seq(-pi, pi, length=50) # creating a vector as a sequence from 0 to 2*pi with 50 entries
my.seq2 <- seq(-0.5*pi, 1.5*pi, length=50) # creating a vector as a sequence from 0 to 2*pi with 50 entries
my.matrix <- outer(sin(my.seq),cos(my.seq2)) # creating the matrix using sin, cos and outer
filled.contour(x=my.seq, y=my.seq2,my.matrix, plot.title=title(main="Products Sin(x)*Cos(y) on [-Pi,Pi]x[-0.5Pi,1.5Pi]", xlab="x", ylab="y"), key.title=title(main="products"), col=terrain.colors(20))