level curves of a surface on a 2D plot
contour2d(x, y, z, nz, [style, strf, leg, rect, nax, fpf]) contour2d(x, y, z, nz, <opt_args>)
two real row vectors of size n1
and
n2
: the grid.
real matrix of size (n1,n2)
, the
values of the function on the grid or a Scilab function which defines the surface z=f(x,y)
.
the level values or the number of levels.
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 |
nz
is a vector
nz(i)
gives the value of
the i
-th level curve.
This represents a sequence of statements
key1=value1, key2=value2
,... where
key1
, key2
,... can
be one of the following: style
,
leg
, rect
,
nax
, strf
or
axesflag
and
frameflag
(see plot2d)
see plot2d. The argument
style
gives the dash styles or colors
which are to be used for level curves. It must have the
same size as the number of levels.
You can change the format of the floating point number printed on
the levels where fpf
is the format in C format syntax
(for example fpf="%.3f"
).
Set fpf
to " " implies that the level are not drawn on the level curves.
If not given, the default format is "%.3g"
.
contour2d
draws level curves of a surface
z=f(x,y)
on a 2D plot. The values of
f(x,y)
are given by the matrix
z
at the grid points defined by
x
and y
.
The optional arguments style
,
strf
, leg
,
rect
, nax
can be
passed by a sequence of statements key1=value1,
key2=value2
,... where keys may be
style
, strf
,
leg
, rect
,
nax
. In this case, the order has no special meaning.
Use contour
to draw levels curves on a 3D surface.
contour2d(1:10,1:10,rand(10,10),5,rect=[0,0,11,11]) | ![]() | ![]() |
clf() // changing the format of the printing of the levels contour2d(1:10,1:10,rand(10,10),5,rect=[0,0,11,11],fpf="%.2f") | ![]() | ![]() |
// now an example with level numbers drawn in a legend // Caution there are a number of tricks... x = linspace(0,4*%pi,80); z = cos(x')*cos(x); clf(); f=gcf(); // trick 1: fpf=" " implies that the level numbers are not // drawn on the level curves f.color_map=jet(7); // trick 2: to be able to put the legend on the right without // interfering with the level curves use rect with a xmax // value large enough contour2d(x,x,z,-0.75:0.25:0.75,frameflag=3,rect=[0,0,5*%pi,4*%pi],fpf=" ") // trick 3: use legends (note that the more practical legend function // will not work as soon as one of the level is formed by 2 curves) legends(string(-0.75:0.25:0.75),1:7,"lr"); xtitle("Some level curves of the function cos(x)cos(y)") | ![]() | ![]() |