contour

level curves on a 3D surface

Calling Sequence

contour(x,y,z,nz,[theta,alpha,leg,flag,ebox,zlev])
contour(x,y,z,nz,<opt_args>)

Arguments

:x,y two real row vectors of size n1 and n2. : :z real matrix of size (n1,n2), the values of the function or a

Scilab function which defines the surface z=f(x,y).

: :nz the level values or the number of levels.

:- If nz is an integer, its value gives the number of level curves equally spaced from zmin to zmax as follows:

    z= zmin + (1:nz)*(zmax-zmin)/(nz+1)

Note that the `zmin` and `zmax` levels are not drawn (generically they
are reduced to points) but they can be added with

    [im,jm] = `find`_(z == zmin);     // or zmax
    `plot2d`_(x(im)',y(jm)',-9,"000")


: :- If `nz` is a vector, `nz(i)` gives the value of the ith level
  curve. Note that it can be useful in order to see `zmin` and `zmax`
  level curves to add an epsilon tolerance:
  `nz=[zmin+%eps,..,zmax-%eps]`.
:

: :<opt_args> a sequence of statements key1=value1, key2=value2, ...

where keys may be theta, alpha, leg, flag, ebox, zlev (see below). In this case, the order has no special meaning.

: :theta, alpha real values giving in degree the spherical coordinates

of the observation point.

: :leg string defining the captions for each axis with @ as a field

separator, for example “X@Y@Z”.

: :flag a real vector of size three flag=[mode,type,box].

:mode string representation mode.

mode=0:the level curves are drawn on the surface defined by (x,y,z).

: :mode=1: the level curves are drawn on a 3D plot and on the plan

defined by the equation z=zlev.

: :mode=2: the level curves are drawn on a 2D plot. :

: :type an integer (scaling).

:type=0 the plot is made using the current 3D scaling (set by a

previous call to param3d, plot3d, contour or plot3d1).

: :type=1 rescales automatically 3d boxes with extreme aspect ratios,

the boundaries are specified by the value of the optional argument ebox.

: :type=2 rescales automatically 3d boxes with extreme aspect ratios,

the boundaries are computed using the given data.

: :type=3 3d isometric with box bounds given by optional ebox,

similarily to type=1

: :type=4 3d isometric bounds derived from the data, to similarily

type=2

: :type=5 3d expanded isometric bounds with box bounds given by

optional ebox, similarily to type=1

: :type=6 3d expanded isometric bounds derived from the data,

similarily to type=2

:

: :box an integer (frame around the plot).

:box=0 nothing is drawn around the plot. : :box=1 unimplemented (like box=0). : :box=2 only the axes behind the surface are drawn. : :box=3 a box surrounding the surface is drawn and captions are

added.

: :box=4 a box surrounding the surface is drawn, captions and axes are

added.

:

:

: :ebox used when type in flag is 1. It specifies the boundaries

of the plot as the vector [xmin,xmax,ymin,ymax,zmin,zmax].

: :zlev real number. :

Description

contour draws level curves of a surface z=f(x,y). The level curves are drawn on a 3D surface. The optional arguments are the same as for the function plot3d (except zlev) and their meanings are the same. They control the drawing of level curves on a 3D plot. Only flag(1)=mode has a special meaning.

:mode=0 the level curves are drawn on the surface defined by (x,y,z). : :mode=1 the level curves are drawn on a 3D plot and on the plan

defined by the equation z=zlev.

: :mode=2 the level curves are drawn on a 2D plot. :

You can change the format of the floating point number printed on the levels by using xset(“fpf”,string) where string gives the format in C format syntax (for example string=”%.3f”). Use string=”“ to switch back to default format and Use string=” “ to suppress printing.

Usually we use contour2d to draw levels curves on a 2D plot.

Enter the command contour() to see a demo.

Sample

Examples

t=`linspace`_(-%pi,%pi,30);
function z=my_surface(x, y),z=x*`sin`_(x)^2*`cos`_(y),endfunction

contour(t,t,my_surface,10)
// changing the format of the printing of the levels
`xset`_("fpf","%.1f")
`clf`_()
contour(t,t,my_surface,10)
// 3D
`clf`_()
z=`feval`_(t,t,my_surface);
`plot3d`_(t,t,z);contour(t,t,z+0.2*`abs`_(z),20,flag=[0 2 4]);

See Also

• contour2d level curves of a surface on a 2D plot
• plot3d 3D plot of a surface