# Sfgrayplot

smooth 2D plot of a surface defined by a function using colors

## Calling Sequence

                Sfgrayplot(x, y, f, <opt_args>)
                Sfgrayplot(x, y, f [,strf, rect, nax, zminmax, colminmax, mesh, colout])

## Arguments

x, y

  real row vectors of size `n1` and `n2`.

f

  a scilab function (`z=f(x,y)`).

<opt_args>

  this represents a sequence of statements `key1=value1, key2=value2, ...` where `key1`, `key2, ...` can be one of the following: `strf`, `rect`, `nax`, `zminmax`, `colminmax`, `mesh`, `colout` (see plot2d for the 3 first and fec for the 4 last).

strf, rect, nax

  see plot2d.

zminmax, colminmax, mesh, colout

  see fec.

## Description

`Sfgrayplot` is the same as `fgrayplot` but the plot is smoothed. The function `fec` is used for smoothing. The surface is plotted assuming that it is linear on a set of triangles built from the grid (here with `n1=5`, `n2=3`):

    _____________
    | /| /| /| /|
    |/_|/_|/_|/_|
    | /| /| /| /|
    |/_|/_|/_|/_|

The function colorbar may be used to see the color scale (but you must know (or compute) the min and max values).

Instead of `Sfgrayplot`, you can use Sgrayplot and this may be a little faster.

Enter the command `Sfgrayplot()` to see a demo.

## Examples

    // example #1: plot 4 surfaces
    function z=surf1(x,y), z=x*y, endfunction
    function z=surf2(x,y), z=x^2-y^2, endfunction
    function z=surf3(x,y), z=x^3+y^2, endfunction
    function z=surf4(x,y), z=x^2+y^2, endfunction
    clf()
    set(gcf(),"color_map",[jetcolormap(64);hotcolormap(64)])
    x = linspace(-1,1,60);
    y = linspace(-1,1,60);
    drawlater();
    subplot(2,2,1)
      colorbar(-1,1,[1,64])
      Sfgrayplot(x,y,surf1,strf="041",colminmax=[1,64])
      xtitle("f(x,y) = x*y")
    subplot(2,2,2)
      colorbar(-1,1,[65,128])
      Sfgrayplot(x,y,surf2,strf="041",colminmax=[65,128])
      xtitle("f(x,y) = x^2-y^2")
    subplot(2,2,3)
      colorbar(-1,2,[65,128])
      Sfgrayplot(x,y,surf3,strf="041",colminmax=[65,128])
      xtitle("f(x,y) = x^3+y^2")
    subplot(2,2,4)
      colorbar(0,2,[1,64])
      Sfgrayplot(x,y,surf4,strf="041",colminmax=[1,64])
      xtitle("f(x,y) = x^2+y^2")
    drawnow();
    show_window()

function z=surf1(x,y), z=x*y, endfunction function z=surf2(x,y), z=x^2-y^2, endfunction function z=surf3(x,y), z=x^3+y^2, endfunction function z=surf4(x,y), z=x^2+y^2, endfunction clf() set(gcf(),"color_map",[jetcolormap(64);hotcolormap(64)]) x = linspace(-1,1,60); y = linspace(-1,1,60); drawlater(); subplot(2,2,1) colorbar(-1,1,[1,64]) Sfgrayplot(x,y,surf1,strf="041",colminmax=[1,64]) xtitle("f(x,y) = x*y") subplot(2,2,2) colorbar(-1,1,[65,128]) Sfgrayplot(x,y,surf2,strf="041",colminmax=[65,128]) xtitle("f(x,y) = x^2-y^2") subplot(2,2,3) colorbar(-1,2,[65,128]) Sfgrayplot(x,y,surf3,strf="041",colminmax=[65,128]) xtitle("f(x,y) = x^3+y^2") subplot(2,2,4) colorbar(0,2,[1,64]) Sfgrayplot(x,y,surf4,strf="041",colminmax=[1,64]) xtitle("f(x,y) = x^2+y^2") drawnow();

    // example #2: plot surf3 and add some contour lines
    function z=surf3(x,y), z=x^3+y^2, endfunction
    clf()
    x = linspace(-1,1,60);
    y = linspace(-1,1,60);
    set(gcf(),"color_map",hotcolormap(128))
    drawlater();
    colorbar(-1,2)
    Sfgrayplot(x,y,surf3,strf="041")
    contour2d(x,y,surf3,[-0.1, 0.025, 0.4],style=[1 1 1],strf="000")
    xtitle("f(x,y) = x^3+y^2")
    drawnow();
    show_window()

function z=surf3(x,y), z=x^3+y^2, endfunction clf() x = linspace(-1,1,60); y = linspace(-1,1,60); set(gcf(),"color_map",hotcolormap(128)) drawlater(); colorbar(-1,2) Sfgrayplot(x,y,surf3,strf="041") contour2d(x,y,surf3,[-0.1, 0.025, 0.4],style=[1 1 1],strf="000") xtitle("f(x,y) = x^3+y^2") drawnow() ; show_window()

    // example #3: plot surf3 and use zminmax and colout optional arguments
    //             to restrict the plot for -0.5<= z <= 1
    function z=surf3(x,y), z=x^3+y^2, endfunction
    clf()
    x = linspace(-1,1,60);
    y = linspace(-1,1,60);
    set(gcf(),"color_map",jetcolormap(128))
    drawlater();
    zminmax = [-0.5 1]; colors=[32 96];
    colorbar(zminmax(1),zminmax(2),colors)
    Sfgrayplot(x, y, surf3, strf="041", zminmax=zminmax, colout=[0 0], colminmax=colors)
    contour2d(x,y,surf3,[-0.5, 1],style=[1 1 1],strf="000")
    xtitle("f(x,y) = x^3+y^2, with parts under z = -0.5 and upper z = 1 removed")
    drawnow() ;
    show_window()

function z=surf3(x,y), z=x^3+y^2, endfunction clf() x = linspace(-1,1,60); y = linspace(-1,1,60); set(gcf(),"color_map",jetcolormap(128)) drawlater() ; zminmax = [-0.5 1]; colors=[32 96]; colorbar(zminmax(1),zminmax(2),colors) Sfgrayplot(x, y, surf3, strf="041", zminmax=zminmax, colout=[0 0], colminmax=colors) contour2d(x,y,surf3,[-0.5, 1],style=[1 1 1],strf="000") xtitle("f(x,y) = x^3+y^2, with parts under z = -0.5 and upper z = 1 removed") drawnow() ; show_window()

## See Also

- fec
- fgrayplot
- grayplot
- Sgrayplot