semilogy
Semilog plot (y-axis has log scale)
Syntax
Description
Vector and Matrix Data
semilogy(
plots
x- and y-coordinates using a linear scale on the
x-axis and a base-10 logarithmic scale on the y-axis.X
,Y
)
To plot a set of coordinates connected by line segments, specify
X
andY
as vectors of the same length.To plot multiple sets of coordinates on the same set of axes, specify at least one of
X
orY
as a matrix.
semilogy(
plots Y
)Y
against an implicit set of x-coordinates.
If
Y
is a vector, the x-coordinates range from 1 tolength(Y)
.If
Y
is a matrix, the plot contains one line for each column inY
. The x-coordinates range from 1 to the number of rows inY
.
If Y
contains complex numbers,
semilogy
plots the imaginary part of Y
versus
the real part of Y
. However, if you specify both X
and Y
, MATLAB® ignores the imaginary part.
Table Data
semilogy(
plots the variables tbl
,xvar
,yvar
)xvar
and yvar
from the table
tbl
. To plot one data set, specify one variable for
xvar
and one variable for yvar
. To plot multiple
data sets, specify multiple variables for xvar
,
yvar
, or both. If both arguments specify multiple variables, they must
specify the same number of variables. (since R2022a)
Additional Options
semilogy(
displays the
plot in the target axes. Specify the axes as the first argument in any of the previous
syntaxes.ax
,___)
semilogy(___,
specifies Name,Value
)Line
properties using one or more name-value arguments. The
properties apply to all the plotted lines. Specify the name-value arguments after all the
arguments in any of the previous syntaxes. For a list of properties, see Line Properties.
p = semilogy(___)
returns a Line
object or an array of Line
objects. Use p
to modify
properties of the plot after creating it. For a list of properties, see Line Properties.
Examples
Plot One Line
Create a vector of x-coordinates and a vector of y-coordinates. Create a log-linear plot of x
and y
, and call the grid
function to show the grid lines.
x = 1:100;
y = x.^2;
semilogy(x,y)
grid on
Plot Multiple Lines
Create a vector of x-coordinates and two vectors of y-coordinates. Plot two lines by passing comma-separated x-y pairs to semilogy
.
x = 1:100;
y1 = x.^2;
y2 = x.^3;
semilogy(x,y1,x,y2)
grid on
Specify Tick Locations, Tick Labels, and Axis Labels
Define vector x
as the installments on a 20 year loan. Define vector y
as the cumulative cost of a $1000 loan with an interest rate of 8%. Plot the cumulative cost at each installment.
P = 1000;
npayments = 240;
rate = 0.08/12;
mpayment = P*(rate*(1+rate)^npayments)/(((1+rate)^npayments) - 1);
x = 1:240;
y = x * mpayment;
semilogy(x,y);
grid on
Change the y-axis tick values and tick labels by calling the yticks
and yticklabels
functions. Then create x- and y-axis labels by calling the xlabel
and ylabel
functions.
yticks([10 50 100 500 1000]) yticklabels({'$10','$50','$100','$500','$1000'}) xlabel ('Installment') ylabel('Cumulate Cost')
Plot Points as Markers Without Lines
Create a set of x- and y-coordinates and plot them in a log-linear plot. Specify the line style as 'o'
to display circular markers without connecting lines. Specify the marker fill color as the RGB triplet [0 0.447 0.741]
, which corresponds to a dark shade of blue.
x = linspace(1,1000,15); y = (1./x) * 10000; semilogy(x,y,'o','MarkerFaceColor',[0 0.447 0.741]) grid on
Add a Legend
Create two sets of x- and y-coordinates and display them in a log-linear plot. Specify a dashed line for the first set of coordinates. Then display a legend in the upper left corner of the plot by calling the legend
function and specifying the location as 'northwest'
.
x = 1:100; y1 = x.^2; y2 = x.^3; semilogy(x,y1,'--',x,y2) legend('x^2','x^3','Location','northwest')
Specify y-Coordinates Only
When you specify only one coordinate vector, semilogy
plots those coordinates against the values 1:length(y)
. For example, define y
as a vector of 5 values. Create a log-linear plot of y.
y = [0.1 0.2 1 10 1000];
semilogy(y)
grid on
If you specify y
as a matrix, the columns of y are plotted against the values 1:size(y,1)
. For example, define y
as a 5-by-3 matrix and pass it to the semilogy
function. The resulting plot contains 3 lines, each of which has x-coordinates that range from 1
to 5
.
y = [ 0.1 1 10
0.2 2 20
1.0 10 100
10 100 1000
1000 10000 100000];
semilogy(y)
grid on
Plot Coordinates from a Table
Since R2022a
A convenient way to plot data from a table is to pass the table to the semilogy
function and specify the variables to plot.
Create a table containing two variables. Then display the first three rows of the table.
Input = (1:100)'; Output = Input.^2; tbl = table(Input,Output); head(tbl,3)
Input Output _____ ______ 1 1 2 4 3 9
Plot the Input
variable on the x-axis and the Output
variable on the y-axis. Return the Line
object as p
, and turn the axes grid on. Notice that the axis labels match the variable names.
p = semilogy(tbl,"Input","Output"); grid on
To modify aspects of the line, set the LineStyle
, Color
, and Marker
properties on the Line
object. For example, change the line to a red dotted line with point markers.
p.LineStyle = ":"; p.Color = "red"; p.Marker = ".";
Plot Multiple Table Variables on One Axis
Since R2022a
Create a table containing three variables. Then display the first three rows in the table.
Input = (1:100)'; Output1 = Input.^2; Output2 = Input.^3; tbl = table(Input,Output1,Output2); head(tbl,3)
Input Output1 Output2 _____ _______ _______ 1 1 1 2 4 8 3 9 27
Plot the Input
variable on the x-axis and the Output1
and Output2
variables on the y-axis. Add a legend. Notice that the legend labels match the variable names.
semilogy(tbl,"Input",["Output1","Output2"]) grid on legend
Specify Target Axes
Create a tiled chart layout in the 'flow'
tile arrangement, so that the axes fill the available space in the layout. Next, call the nexttile
function to create an axes object and return it as ax1
. Then display a log-linear plot by passing ax1
to the semilogy
function.
tiledlayout('flow')
ax1 = nexttile;
x = 1:100;
y1 = x.^2;
semilogy(ax1,x,y1)
Repeat the process to create a second log-linear plot.
ax2 = nexttile; y2 = 1./x; semilogy(ax2,x,y2)
Change Line Appearance After Plotting
Create a log-linear plot containing two lines, and return the line objects in the variable slg
.
x = 1:100; y1 = x.^2; y2 = x.^3; slg = semilogy(x,y1,x,y2);
Change the width of the first line to 3
, and change the color of the second line to purple.
slg(1).LineWidth = 3; slg(2).Color = [0.4 0 1];
Plot Discontinuous Function
Insert NaN
values wherever there are discontinuities in your data. The semilogy
function displays gaps at those locations.
Create a pair of x- and y-coordinate vectors. Replace the twentieth y-coordinate with a NaN
value. Then create a log-linear plot of x
and y
.
x = 1:50; y = x.^2; y(20) = NaN; semilogy(x,y)
Input Arguments
X
— Linear scale coordinates
scalar | vector | matrix
Linear scale coordinates, specified as a scalar, vector, or matrix. The size and
shape of X
depends on the shape of your data and the type of plot you
want to create. This table describes the most common situations.
Type of Plot | How to Specify Coordinates |
---|---|
Single point | Specify semilogy(1,2,'o') |
One set of points | Specify semilogy([1 2 3],[4; 5; 6]) |
Multiple sets of points (using vectors) | Specify consecutive pairs of semilogy([1 2 3],[4 5 6],[1 2 3],[7 8 9]) |
Multiple sets of points (using matrices) | If all the sets share the same x- or y-coordinates, specify the shared coordinates as a vector and the other coordinates as a matrix. The length of the vector must match one of the dimensions of the matrix. For example: semilogy([1 2 3],[4 5 6; 7 8 9]) semilogy plots one line for each
column in the matrix. Alternatively, specify
semilogy([1 2 3; 4 5 6],[7 8 9; 10 11 12]) |
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
| categorical
| datetime
| duration
Y
— Log scale coordinates
scalar | vector | matrix
Log scale coordinates, specified as a scalar, vector, or matrix. The size and shape
of Y
depends on the shape of your data and the type of plot you want
to create. This table describes the most common situations.
Type of Plot | How to Specify Coordinates |
---|---|
Single point | Specify semilogy(1,2,'o') |
One set of points | Specify semilogy([1 2 3],[4; 5; 6]) |
Multiple sets of points (using vectors) | Specify consecutive pairs of semilogy([1 2 3],[4 5 6],[1 2 3],[7 8 9]) |
Multiple sets of points (using matrices) | If all the sets share the same x- or y-coordinates, specify the shared coordinates as a vector and the other coordinates as a matrix. The length of the vector must match one of the dimensions of the matrix. For example: semilogy([1 2 3],[4 5 6; 7 8 9]) semilogy plots one line for each
column in the matrix.Alternatively, specify
semilogy([1 2 3; 4 5 6],[7 8 9; 10 11 12]) |
semilogy
might exclude coordinates in some cases:
If the log scale coordinates include positive and negative values, only the positive values are displayed.
If the log scale coordinates are all negative, all of the values are displayed on a log scale with the appropriate sign.
Log scale values of zero are not displayed.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
LineSpec
— Line style, marker, and color
string scalar | character vector
Line style, marker, and color, specified as a string scalar or character vector containing symbols. The symbols can appear in any order. You do not need to specify all three characteristics (line style, marker, and color). For example, if you omit the line style and specify the marker, then the plot shows only the marker and no line.
Example: "--or"
is a red dashed line with circle markers.
Line Style | Description | Resulting Line |
---|---|---|
"-" | Solid line |
|
"--" | Dashed line |
|
":" | Dotted line |
|
"-." | Dash-dotted line |
|
Marker | Description | Resulting Marker |
---|---|---|
"o" | Circle |
|
"+" | Plus sign |
|
"*" | Asterisk |
|
"." | Point |
|
"x" | Cross |
|
"_" | Horizontal line |
|
"|" | Vertical line |
|
"square" | Square |
|
"diamond" | Diamond |
|
"^" | Upward-pointing triangle |
|
"v" | Downward-pointing triangle |
|
">" | Right-pointing triangle |
|
"<" | Left-pointing triangle |
|
"pentagram" | Pentagram |
|
"hexagram" | Hexagram |
|
Color Name | Short Name | RGB Triplet | Appearance |
---|---|---|---|
"red" | "r" | [1 0 0] |
|
"green" | "g" | [0 1 0] |
|
"blue" | "b" | [0 0 1] |
|
"cyan"
| "c" | [0 1 1] |
|
"magenta" | "m" | [1 0 1] |
|
"yellow" | "y" | [1 1 0] |
|
"black" | "k" | [0 0 0] |
|
"white" | "w" | [1 1 1] |
|
tbl
— Source table
table | timetable
Source table containing the data to plot, specified as a table or a timetable.
xvar
— Table variables containing x-coordinates
character vector | string array | cell array | pattern | numeric scalar or vector | logical vector | vartype()
Table variables containing the x-coordinates, specified using one of the indexing schemes from the table.
Indexing Scheme | Examples |
---|---|
Variable names:
|
|
Variable index:
|
|
Variable type:
|
|
The table variables you specify can contain numeric, categorical, datetime, or
duration values. If xvar
and yvar
both specify
multiple variables, the number of variables must be the same.
Example: semilogy(tbl,["x1","x2"],"y")
specifies the table
variables named x1
and x2
for the
x-coordinates.
Example: semilogy(tbl,2,"y")
specifies the second variable for the
x-coordinates.
Example: semilogy(tbl,vartype("numeric"),"y")
specifies all
numeric variables for the x-coordinates.
yvar
— Table variables containing y-coordinates
character vector | string array | cell array | pattern | numeric scalar or vector | logical vector | vartype()
Table variables containing the y-coordinates, specified using one of the indexing schemes from the table.
Indexing Scheme | Examples |
---|---|
Variable names:
|
|
Variable index:
|
|
Variable type:
|
|
The table variables you specify can contain any numeric values. However,
semilogy
might exclude negative and zero values from the plot in
the same way as it does when you specify Y
as a vector containing
negative or zero values.
If xvar
and yvar
both specify multiple
variables, the number of variables must be the same.
Example: semilogy(tbl,"x",["y1","y2"])
specifies the table
variables named y1
and y2
for the
y-coordinates.
Example: semilogy(tbl,"x",2)
specifies the second variable for the
y-coordinates.
Example: semilogy(tbl,"x",vartype("numeric"))
specifies all
numeric variables for the y-coordinates.
ax
— Target axes
Axes
object
Target axes, specified as an Axes
object. If you do not specify
the axes and if the current axes is Cartesian, then semilogy
uses the
current axes.
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: semilogy([1 2],[3 4],'Color','red')
specifies a red line for
the plot.
Note
The properties listed here are only a subset. For a complete list, see Line Properties.
Color
— Color
[0 0.4470 0.7410]
(default) | RGB triplet | hexadecimal color code | 'r'
| 'g'
| 'b'
| ...
Color, specified as an RGB triplet, a hexadecimal color code, a color name, or a
short name. The color you specify sets the line color. It also sets the marker edge
color when the MarkerEdgeColor
property is set to
'auto'
.
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.
MarkerSize
— Marker size
6
(default) | positive value
Marker size, specified as a positive value in points, where 1 point = 1/72 of an inch.
MarkerEdgeColor
— Marker outline color
"auto"
(default) | RGB triplet | hexadecimal color code | "r"
| "g"
| "b"
| ...
Marker outline color, specified as "auto"
, an RGB triplet, a
hexadecimal color code, a color name, or a short name. The default value of
"auto"
uses the same color as the Color
property.
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" |
MarkerFaceColor
— Marker fill color
"none"
(default) | "auto"
| RGB triplet | hexadecimal color code | "r"
| "g"
| "b"
| ...
Marker fill color, specified as "auto"
, an RGB triplet, a hexadecimal
color code, a color name, or a short name. The "auto"
option uses the
same color as the Color
property of the parent axes. If you specify
"auto"
and the axes plot box is invisible, the marker fill color is
the color of the figure.
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" |
Tips
The
semilogy
function uses colors and line styles based on theColorOrder
andLineStyleOrder
properties of the axes.semilogy
cycles through the colors with the first line style. Then, it cycles through the colors again with each additional line style.You can change the colors and the line styles after plotting by setting the
ColorOrder
orLineStyleOrder
properties on the axes. You can also call thecolororder
function to change the color order for all the axes in the figure.
Algorithms
The semilogy
function plots y-coordinates on a log
scale by setting the YScale
property of the axes to
'log'
. However, if the axes hold
state is 'on'
before you call
semilogy
, the property does not change, and the
y-coordinates might display on a linear scale.
Extended Capabilities
GPU Arrays
Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.
The semilogy
function
supports GPU array input with these usage notes and limitations:
This function accepts GPU arrays, but does not run on a GPU.
For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).
Distributed Arrays
Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.
Usage notes and limitations:
This function operates on distributed arrays, but executes in the client MATLAB.
For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).
Version History
Introduced before R2006aR2022b: Plots created with tables preserve special characters in axis and legend labels
When you pass a table and one or more variable names to the semilogy
function, the axis and legend labels now display any special characters that are included in the table variable names, such as underscores. Previously, special characters were interpreted as TeX or LaTeX characters.
For example, if you pass a table containing a variable named Sample_Number
to the semilogy
function, the underscore appears in the axis and
legend labels. In R2022a and earlier releases, the underscores are interpreted as
subscripts.
Release | Label for Table Variable "Sample_Number" |
---|---|
R2022b |
|
R2022a |
|
To display axis and legend labels with TeX or LaTeX formatting, specify the labels manually.
For example, after plotting, call the xlabel
or
legend
function with the desired label strings.
xlabel("Sample_Number") legend(["Sample_Number" "Another_Legend_Label"])
R2022a: Pass tables directly to semilogy
Create plots by passing a table to the semilogy
function followed by the variables you want to plot. When you specify your data as a table, the axis labels and the legend (if present) are automatically labeled using the table variable names.
See Also
Functions
Properties
MATLAB Command
You clicked a link that corresponds to this MATLAB command:
Run the command by entering it in the MATLAB Command Window. Web browsers do not support MATLAB commands.
Select a Web Site
Choose a web site to get translated content where available and see local events and offers. Based on your location, we recommend that you select: .
You can also select a web site from the following list:
How to Get Best Site Performance
Select the China site (in Chinese or English) for best site performance. Other MathWorks country sites are not optimized for visits from your location.
Americas
- América Latina (Español)
- Canada (English)
- United States (English)
Europe
- Belgium (English)
- Denmark (English)
- Deutschland (Deutsch)
- España (Español)
- Finland (English)
- France (Français)
- Ireland (English)
- Italia (Italiano)
- Luxembourg (English)
- Netherlands (English)
- Norway (English)
- Österreich (Deutsch)
- Portugal (English)
- Sweden (English)
- Switzerland
- United Kingdom (English)