gnuplot画heatmap图（灰色系）

set cbrange [0:2]
set palette defined (0 "gray100",20 "gray80",40 "gray60",60 "gray40",\
    80 "gray20",100 "gray0",101 "grey0")
plot 'test.dat' u 1:2:3 w image

reset

效果如图：

生成"test.dat"的Fortran程序：

        program HelloWorld
        integer,parameter :: grid=20
        integer i, j
        real x(grid,grid), y(grid,grid), heat(grid,grid)       
        
        OPEN(10,file="test.dat")
        write(10,200)"#x","y","heat"
200     format(3A12)

        do i=1,grid

          do j=1,grid
            x(i,j)=-1.0+(i-1)*2.0/real(grid)
            y(i,j)=-1.0+(j-1)*2.0/real(grid)
            heat(i,j)=x(i,j)**2+y(i,j)**2
            write(10,*)x(i,j),y(i,j),heat(i,j)
          end do
        end do
        CLOSE(10)
        
        STOP
        end