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# contour2d

level curves of a surface on a 2D plot

### Syntax

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 with- If
`nz`

is a vector `nz(i)`

gives the value of the`i`

-th level curve.

- If
- <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])

clf() // changing the format of the printing of the levels xset("fpf","%.2f") 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 — compute level curves of a surface on a 2D plot
- contour2dm — compute level curves of a surface defined with a mesh
- plot2d — 2D plot

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