fcontour
Plot contours
Syntax
Description
fcontour(
plots
the contour lines of the function f
)z = f(x,y)
for
constant levels of z
over the default interval [-5
5]
for x
and y
.
fcontour(
plots
over the specified interval. To use the same interval for both f
,xyinterval
)x
and y
,
specify xyinterval
as a two-element vector of
the form [min max]
. To use different intervals,
specify a four-element vector of the form [xmin xmax ymin
ymax]
.
fcontour(___,
sets
the line style and color for the contour lines. For example, LineSpec
)'-r'
specifies
red lines. Use this option after any of the previous input argument
combinations.
fcontour(___,
specifies
line properties using one or more name-value pair arguments.Name,Value
)
fcontour(
plots
into the axes specified by ax
,___)ax
instead of the
current axes.
returns
a fc
= fcontour(___)FunctionContour
object. Use fc
to
query and modify properties of a specific FunctionContour
object.
For a list of properties, see FunctionContour Properties.
Examples
Plot Contours of Function
Plot the contours of over the default interval of and .
f = @(x,y) sin(x) + cos(y); fcontour(f)
Specify Plotting Interval and Plot Piecewise Contour Plot
Specify the plotting interval as the second argument of fcontour
. When you plot multiple inputs over different intervals in the same axes, the axis limits adjust to display all the data. This behavior lets you plot piecewise inputs.
Plot the piecewise input
over .
fcontour(@(x,y) erf(x) + cos(y),[-5 0 -5 5]) hold on fcontour(@(x,y) sin(x) + cos(y),[0 5 -5 5]) hold off grid on
Change Line Style and Width
Plot the contours of as dashed lines with a line width of 2
.
f = @(x,y) x.^2 - y.^2; fcontour(f,'--','LineWidth',2)
Plot Multiple Contour Plots
Plot and on the same axes by using hold on
.
fcontour(@(x,y) sin(x)+cos(y)) hold on fcontour(@(x,y) x-y) hold off
Modify Contour Plot After Creation
Plot the contours of . Assign the function contour object to a variable.
f = @(x,y) exp(-(x/3).^2-(y/3).^2) + exp(-(x+2).^2-(y+2).^2); fc = fcontour(f)
fc = FunctionContour with properties: Function: @(x,y)exp(-(x/3).^2-(y/3).^2)+exp(-(x+2).^2-(y+2).^2) LineColor: 'flat' LineStyle: '-' LineWidth: 0.5000 Fill: off LevelList: [0.2000 0.4000 0.6000 0.8000 1 1.2000 1.4000] Use GET to show all properties
Change the line width to 1
and the line style to a dashed line by using dot notation to set properties of the function contour object. Show contours close to 0
and 1
by setting the LevelList
property. Add a colorbar.
fc.LineWidth = 1;
fc.LineStyle = '--';
fc.LevelList = [1 0.9 0.8 0.2 0.1];
colorbar
Fill Area Between Contours
Create a plot that looks like a sunset by filling the area between the contours of
f = @(x,y) erf((y+2).^3) - exp(-0.65*((x-2).^2+(y-2).^2)); fcontour(f,'Fill','on');
If you want interpolated shading instead, use the fsurf
function and set its 'EdgeColor'
option to 'none'
followed by the command view(0,90)
.
Specify Levels for Contour Lines
Set the values at which fcontour
draws contours by using the 'LevelList'
option.
f = @(x,y) sin(x) + cos(y);
fcontour(f,'LevelList',[-1 0 1])
Control Resolution of Contour Lines
Control the resolution of contour lines by using the 'MeshDensity'
option. Increasing 'MeshDensity'
can make smoother, more accurate plots, while decreasing it can increase plotting speed.
Create two plots in a 2-by-1 tiled chart layout. In the first plot, display the contours of . The corners of the squares do not meet. To fix this issue, increase 'MeshDensity'
to 200
in the second plot. The corners now meet, showing that by increasing 'MeshDensity'
you increase the resolution.
f = @(x,y) sin(x).*sin(y); tiledlayout(2,1) nexttile fcontour(f) title('Default Mesh Density (71)') nexttile fcontour(f,'MeshDensity',200) title('Custom Mesh Density (200)')
Add Title and Axis Labels and Format Ticks
Plot . Display the grid lines, add a title, and add axis labels.
fcontour(@(x,y) x.*sin(y) - y.*cos(x), [-2*pi 2*pi], 'LineWidth', 2); grid on title({'xsin(y) - ycos(x)','-2\pi < x < 2\pi and -2\pi < y < 2\pi'}) xlabel('x') ylabel('y')
Set the x-axis tick values and associated labels by setting the XTickLabel
and XTick
properties of the axes object. Access the axes object using gca
. Similarly, set the y-axis tick values and associated labels.
ax = gca; ax.XTick = ax.XLim(1):pi/2:ax.XLim(2); ax.XTickLabel = {'-2\pi','-3\pi/2','-\pi','-\pi/2','0',... '\pi/2','\pi','3\pi/2','2\pi'}; ax.YTick = ax.YLim(1):pi/2:ax.YLim(2); ax.YTickLabel = {'-2\pi','-3\pi/2','-\pi','-\pi/2','0',... '\pi/2','\pi','3\pi/2','2\pi'};
Input Arguments
f
— Function to plot
function handle
Function to plot, specified as a function handle to a named or anonymous function.
Specify a function of the form z = f(x,y)
.
The function must accept two matrix input arguments and return a matrix
output argument of the same size. Use array operators instead of matrix
operators for the best performance. For example, use .*
(times
)
instead of * (mtimes
).
Example: f = @(x,y) sin(x) + cos(y);
xyinterval
— Plotting interval for x
and y
[–5 5 -5 5]
(default) | vector of form [min max]
| vector of form [xmin xmax ymin ymax]
Plotting interval for x
and y
,
specified in one of these forms:
Vector of form
[min max]
— Use the interval[min max]
for bothx
andy
.Vector of form
[xmin xmax ymin ymax]
— Use the interval[xmin xmax]
forx
and[ymin ymax]
fory
.
ax
— Axes object
axes object
Axes object. If you do not specify an axes object, then the fcontour
uses
the current axes.
LineSpec
— Line style and color
character vector | string
Line style and color, specified as a character vector or string containing a line style specifier, a color specifier, or both.
Example: '--r'
specifies red dashed lines
These two tables list the line style and color options.
Line Style Specifier | Description |
---|---|
- | Solid line (default) |
-- | Dashed line |
: | Dotted line |
-. | Dash-dot line |
Color Specifier | Description |
---|---|
| yellow |
| magenta |
| cyan |
| red |
| green |
| blue |
| white |
| black |
Name-Value Arguments
Specify optional pairs of arguments as
Name1=Value1,...,NameN=ValueN
, where Name
is
the argument name and Value
is the corresponding value.
Name-value arguments must appear after other arguments, but the order of the
pairs does not matter.
Before R2021a, use commas to separate each name and value, and enclose
Name
in quotes.
Example: 'MeshDensity',30
The properties listed here are only a subset. For a full list, see FunctionContour Properties.
MeshDensity
— Number of evaluation points per direction
71 (default) | number
Number of evaluation points per direction, specified as a number.
The default is 71
. Because fcontour
uses
adaptive evaluation, the actual number of evaluation points is greater.
Example: 30
Fill
— Fill between contour lines
'off'
(default) | on/off logical value
Fill between contour lines, specified as 'on'
or 'off'
,
or as numeric or logical 1
(true
) or
0
(false
). A value of 'on'
is equivalent to true, and 'off'
is equivalent to
false
. Thus, you can use the value of this property as a logical
value. The value is stored as an on/off logical value of type matlab.lang.OnOffSwitchState
.
A value of
'on'
fill the spaces between contour lines with color.A value of
'off'
leaves the spaces between the contour lines unfilled.
LevelList
— Contour levels
vector of z values
Contour levels, specified as a vector of z values. By default,
the fcontour
function chooses values that span
the range of values in the ZData
property.
Setting this property sets the associated mode property to manual.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
LevelStep
— Spacing between contour lines
0
(default) | scalar numeric value
Spacing between contour lines, specified as a scalar numeric
value. For example, specify a value of 2
to draw
contour lines at increments of 2. By default, LevelStep
is
determined by using the ZData
values.
Setting this property sets the associated mode property to 'manual'
.
Example: 3.4
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
LineColor
— Color of contour lines
'flat'
(default) | RGB triplet | hexadecimal color code | 'r'
| 'g'
| 'b'
| ...
Color of contour lines, specified as 'flat'
, an RGB triplet, a
hexadecimal color code, a color name, or a short name. To use a different color for each
contour line, specify 'flat'
. The color is determined by the contour
value of the line, the colormap, and the scaling of data values into the colormap. For
more information on color scaling, see Control Colormap Limits.
To use the same color for all the contour lines, specify an RGB triplet, a hexadecimal color code, a color name, or a short name.
For a custom color, specify an RGB triplet or a hexadecimal color code.
An RGB triplet is a three-element row vector whose elements specify the intensities of the red, green, and blue components of the color. The intensities must be in the range
[0,1]
, for example,[0.4 0.6 0.7]
.A hexadecimal color code is a string scalar or character vector that starts with a hash symbol (
#
) followed by three or six hexadecimal digits, which can range from0
toF
. The values are not case sensitive. Therefore, the color codes"#FF8800"
,"#ff8800"
,"#F80"
, and"#f80"
are equivalent.
Alternatively, you can specify some common colors by name. This table lists the named color options, the equivalent RGB triplets, and hexadecimal color codes.
Color Name | Short Name | RGB Triplet | Hexadecimal Color Code | Appearance |
---|---|---|---|---|
"red" | "r" | [1 0 0] | "#FF0000" | |
"green" | "g" | [0 1 0] | "#00FF00" | |
"blue" | "b" | [0 0 1] | "#0000FF" | |
"cyan"
| "c" | [0 1 1] | "#00FFFF" | |
"magenta" | "m" | [1 0 1] | "#FF00FF" | |
"yellow" | "y" | [1 1 0] | "#FFFF00" | |
"black" | "k" | [0 0 0] | "#000000" | |
"white" | "w" | [1 1 1] | "#FFFFFF" | |
"none" | Not applicable | Not applicable | Not applicable | No color |
Here are the RGB triplets and hexadecimal color codes for the default colors MATLAB® uses in many types of plots.
RGB Triplet | Hexadecimal Color Code | Appearance |
---|---|---|
[0 0.4470 0.7410] | "#0072BD" | |
[0.8500 0.3250 0.0980] | "#D95319" | |
[0.9290 0.6940 0.1250] | "#EDB120" | |
[0.4940 0.1840 0.5560] | "#7E2F8E" | |
[0.4660 0.6740 0.1880] | "#77AC30" | |
[0.3010 0.7450 0.9330] | "#4DBEEE" | |
[0.6350 0.0780 0.1840] | "#A2142F" |
LineWidth
— Line width
0.5
(default) | positive value
Line width, specified as a positive value in points, where 1 point = 1/72 of an inch. If the line has markers, then the line width also affects the marker edges.
The line width cannot be thinner than the width of a pixel. If you set the line width to a value that is less than the width of a pixel on your system, the line displays as one pixel wide.
Output Arguments
fc
— One or more FunctionContour
objects
scalar | vector
One or more FunctionContour
objects, returned
as a scalar or a vector. You can use these objects to query and modify
the properties of a specific contour plot. For a list of properties,
see FunctionContour Properties.
Version History
Introduced in R2016a
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