So say I have the 2d following matrix:
a = [1,2,3,4,5;
1,2,3,4,5;
1,2,3,4,5;
1,2,3,4,5]
and another matrix with the following values:
b = [0.3,0.4,0.6,0.9,1.2]
Not, I need to plot all the column vectors in a. I can very easily do this with :
plot(a)
However, I want a legend on the side which also shows just which line in the plot corresponds to what value from b.
I've done this using:
legend(b)
after the plot line. However, I wasn't sure if this is plotting the correct correspondence as in the first line color in the legend from b is pointing to the first line in a. Could someone tell me if I am right or at least rectify what I'm doing in that case.
You can get a handle from plot and pass it to legend. Also, you need to convert b to strings to use it in legend.
h = plot(a); % returns a vector of handles to the individual plots
legend(h,num2str(b(:)))
Related
This question is quite basic, but I am looking for the best way to do this.
For a plotted line in matlab, how can a few points on the line be marked. I know it is possible to plot directly using marks. But, in case the line has been plotted and the marks are just to differentiate the plots. Instead of selecting a few points and plotting the second time. An example is shown in this figure below
Right after creating the initial plot you can use the command 'hold on' to keep that plot 'live' and then replot the points as markers. For example:
x=1:10;
y=2*x+4;
plot(x,y)
hold on
plot(x,y,'+')
You can use '*', '.' or any other marker instead of '+'.
If you want the markers to be evenly spaced (and your data is not ,originally) you may create an evenly spaced x vector and then, assuming your plot is not too extreme, interpolate the y values and add just the points. For example:
x=[1,1.5,2,2.3,3,4,4.8,5,6.1,6,7,8,9,10];
y=2*x.^2+4;
plot(x,y)
hold on
x_lin=linspace(min(x),max(x),20);
y_lin=interp1(x,y,x_lin,'linear');
plot(x_lin,y_lin,'+')
hold off
With the following result:
If 'linear' doesn't give a good enough result you can try other interpolation methods like 'cubic', 'spline'...
If you don't want to "add" the marked points in a second moment (but I don't think you will have some advantage), consider to
A) use two plot instructions, separating the array of points "to be marked" using
C = setdiff(A,B)
alternatively
B) plot every point in a for cycle with counter i under a condition
%not tested solution
c1 = '.r' %red point, if they are near they seems a line
c2 = '*b' %blue marker
if (marker_condition == true)
plot(x(i), y(i), c2)
else
plot(x(i), y(i), c1)
end
I want to create a 3x3 matrix of plots in MATLAB where each element is a subplot of some corresponding 1000 samples (suppose values are stored in a 3x3x1000 matrix A). I want the subplots to be spaced very close together, and the y axis numbers/labels to only show up for the left subplots and the x axis numbers/labels to only show up for the bottom subplots.
For example, something similar to plotmatrix, except subplot ij would plot A(i,j,:).
plotmatrix example
Is there an easy way to do this in MATLAB? Thanks!
The axes properties of the subplots can be modified to achieve this, but an easier way would be to use a FEX submission called panel. Have a look at its example output:
subplot can do that for you in MATLAB.
h = subplot(3,3,1)
Will split the current figure in a 3 x 3 matrix and creates an axes(area where you plot something) in the 1st cell of the matrix. h is the "handle" to the axes which you can then use to modify the xlabels and ylabels in any way.
Documentation for subplot
Documentation for Axes
I'm trying to plot 2 lines in a single 3D graph. I have 3 coordinate data matrices for each line.
This is my code:
plot3(pathline_x1 , pathline_y1 , pathline_z1,'g');
hold on
plot3(pathline_x1,pathline_y1,pathline_z1,'r');
hold on
From some reason it plots only the last one. Can someone help me plot both lines?
x = [1 2];y=x;
figure;plot(x,y,'r');hold on;plot(x,y,'b');
This will overwrite your line, since x and y are exactly equal.
To see it actually works, plot two different lines:
figure;plot(x,y,'r');hold on;plot(x,y+2,'b');
Note that I have called hold on only once, since it will hold all plots within the figure until you call hold off or open a new figure using figure.
I am trying to plot some data with Matlab R2015a and as the data sets are changing for different plots I want to create the legend (semi-)automatically. I do this with a list of strings (called list) and then
leg = legend(list);
legtxt=findobj(leg,'type','text');
set(legtxt(1),'color','r');
set(legtxt(2),'color','b');
a.s.o. according to the entries.
However, no matter what index I give in the 'set(legtxt(i))' part, Matlab always tells me 'Index exceeds matrix dimensions.' Same, if I create the the legend manually by not using 'legend(list)' but explicitly typing the legend entries. Does anyone know why this happens or how to solve it? Thanks!
You need to use additional outputs from the call to legend. Specifically, check out the 2nd output called icons in the docs.
As for the error, the call to findobj(...) yields an empty vector, so matrix dimensions are indeed exceeded. Indeed (from the docs):
Starting in R2014b, the legend function returns a legend object. In
previous releases it returns an axes object.
So maybe that's why you can't use findobj to fetch legend text...
Anyhow here is how to solve your problem. In this example I create 3 plots and change the color of the text of the 1st and 2nd entry inside the legend:
x = 1:10;
y1 = sin(x);
y2 = cos(x);
y3 = x;
plot(x,y1,'y*',x,y2,'g--',x,y3,'k')
list = {'y1';'y2';'y3'};
%// You want to play with icons and possibly plots.
[leg,icons,plots,str] = legend(list)
set(icons(1),'color','r','FontSize',12)
set(icons(2),'color','b','FontSize',12)
Output:
Of course you can use the plots output to change any property you want of the plots to make them fit with their legend entry.
I am trying to make a contour plot using the following matlab code:
x=linspace(-10,10);
y=linspace(-10,10);
[X,Y]=meshgrid(x,y);
Z=X.^3-Y.^3;
figure
[c,h]=contour(X,Y,Z,[3]);
clabel(c,h)
This gives me the wrong picture actually:
I really don't understand what goes wrong here, because when I do [c,h]=contour(X,Y,Z,[3 0]) for example, it does give me the correct contour plots for the levels 3 and 0, I need help.
If you only give a single number to contour there, it interprets it as the number of contour lines you want and picks the levels automatically. From the docs:
contour(Z,v) draws a contour plot of matrix Z with contour lines at the data values specified in the monotonically increasing vector v. To display a single contour line at a particular value, define v as a two-element vector with both elements equal to the desired contour level. For example, to draw contour lines at level k, use contour(Z,[k k]). Specifying the vector v sets the LevelListMode property to manual.
e.g. to get a single contour at "3", you need to do it this way instead:
figure
[c,h]=contour(X,Y,Z,[3,3]);
clabel(c,h)
The fourth argument of contour can be two things.
If it is an array of numbers (more than 1) then its the contour value you want to show. Else, if its a single value, its the amount of contour lines you want to show.
Example:
x=linspace(-10,10);
y=linspace(-10,10);
[X,Y]=meshgrid(x,y);
Z=X.^3-Y.^3;
figure
subplot(121)
[c,h]=contour(X,Y,Z,[10]);
clabel(c,h)
subplot(122)
[c,h]=contour(X,Y,Z,[1000 -1000 50 -70 3 0]);
clabel(c,h)