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Please note that the recommended version of Scilab is 2024.1.0. This page might be outdated.

See the recommended documentation of this function

# contour2d

level curves of a surface on a 2D plot

### Calling Sequence

contour2d(x,y,z,nz,[style,strf,leg,rect,nax]) contour2d(x,y,z,nz,<opt_args>)

### Arguments

- x,y
two real row vectors of size n1 and n2: the grid.

- z
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)`

.- 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 withIf

`nz`

is a vector,`nz(i)`

gives the value of the ith level curve.

- <opt_args>
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)- style,strf,leg,rect,nax
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.

### Description

`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`

.

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. This
last feature is useful in conjunction with legends to display
the level numbers in a legend and not directly onto the level curves as
usual (see Examples).

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.

### Examples

contour2d(1:10,1:10,rand(10,10),5,rect=[0,0,11,11]) // changing the format of the printing of the levels xset("fpf","%.2f") clf() contour2d(1:10,1:10,rand(10,10),5,rect=[0,0,11,11]) // 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(); xset("fpf"," ") // trick 1: this implies that the level numbers are not // drawn on the level curves f.color_map=jetcolormap(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]) // 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)")

### See Also

- contour — level curves on a 3D surface
- contour2di — calcule les courbes de niveau d'une surface
- plot2d — 2D plot

### Authors

J.Ph.C.

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