If both the x and y axis are numbers, I can display text on the plot by using the functions num2str, cellstr, and strtrim. These functions format the coordinate values into a cell array of strings, which can then be displayed with the function text:
strValues = strtrim(cellstr(num2str(
[X(:) Y(:)],
'(%d,%d)'
)));
text(
X,
Y,
strValues,
'VerticalAlignment',
'bottom'
);
But what if the x axis contains strings instead of numbers?
X=['john' 'jack' 'mary'.....]
Y=[0 1 2 3]
How do I then show the y values on all of the data plots?
You can create the plot with categoricals...
X = categorical( {'john','jack','mary','jack'} );
Y = [1 2 3 3];
figure;
plot( X, Y, '.', 'markersize', 20 );
You can then place text the same as with numeric data
text( categorical({'jack'}), 2, 'test' )
To add the value as a label to all the points, you can use X directly:
text( X, Y + 0.2, cellstr( num2str( Y(:) ) ) )
1st way:
Juse normal plotting (you may need to enumerate your categories first though) and than set the ticks of your axis. This allows maximum flexiblity at the cost of a potential mix-up
set(gca, 'xTick',1:length(X), 'xTickLabel',X)
The first ensures that all ticks are plottet while the second name-value-pair renames those ticks. When it comes to names or longer strings, you may also want to rotate the ticks labels with 'xtickangle'.
The MathWorks uses this workaround even in its examples:
x = linspace(-10,10,200);
y = cos(x);
plot(x,y)
xticks([-3*pi -2*pi -pi 0 pi 2*pi 3*pi])
xticklabels({'-3\pi','-2\pi','-\pi','0','\pi','2\pi','3\pi'})
2nd way: If you have categorial data, you can plot it right away. Have a look at the doc here.
Related
I would like create a Matlab figure with a double X axis (m/s and km/h) with the same plot.
I have found plotyy and - in Matlab reposity - plotyyy, but I am looking for:
A double X axis.
Together below the plot.
My code is very simple:
stem(M(:, 1) .* 3.6, M(:, 3));
grid on
xlabel('Speed (km/h)');
ylabel('Samples');
M(:, 1) is the speed (in m/s), and M(:, 3) is the data.
I would like only a second line, in the bottom, with the speeds in m/s.
You can do something like the following. In comparison to the solution of #Benoit_11 I do use the normal Matlab labels and refer to both axes with handles so the assignments are explicit.
The following code creates an empty x-axis b with the units m/s with a negligible height. After this, the actual plot is drawn in a second axes a located a bit above the other axes and with units km/h. To plot on a specific axes, insert the axes-handle as the first argument of stem. The conversion from m/s to km/h is directly written in the call to stem. Finally, it's needed to set the xlim-property of the both axes to the same values.
% experimental data
M(:,1) = [ 0, 1, 2, 3, 4, 5];
M(:,3) = [12, 10, 15, 12, 11, 13];
% get bounds
xmaxa = max(M(:,1))*3.6; % km/h
xmaxb = max(M(:,1)); % m/s
figure;
% axis for m/s
b=axes('Position',[.1 .1 .8 1e-12]);
set(b,'Units','normalized');
set(b,'Color','none');
% axis for km/h with stem-plot
a=axes('Position',[.1 .2 .8 .7]);
set(a,'Units','normalized');
stem(a,M(:,1).*3.6, M(:,3));
% set limits and labels
set(a,'xlim',[0 xmaxa]);
set(b,'xlim',[0 xmaxb]);
xlabel(a,'Speed (km/h)')
xlabel(b,'Speed (m/s)')
ylabel(a,'Samples');
title(a,'Double x-axis plot');
As a very simple alternative you could also create a 2nd axis (transparent) and put it below the first one so that you only see the x axis.
Example:
clear
clc
close all
x = 1:10;
x2 = x/3.6;
y = rand(size(x));
hP1 = plot(x,y);
a1Pos = get(gca,'Position');
%// Place axis 2 below the 1st.
ax2 = axes('Position',[a1Pos(1) a1Pos(2)-.05 a1Pos(3) a1Pos(4)],'Color','none','YTick',[],'YTickLabel',[]);
%// Adjust limits
xlim([min(x2(:)) max(x2(:))])
text(2.85,0 ,'m/s','FontSize',14,'Color','r')
text(2.85,.05 ,'km/h','FontSize',14,'Color','r')
Output:
Then you can manually add the x labels for each unit, in different color for example.
The best way i can think to do it is to use 2 plots, for example, you can split the plot into a large and small section by doing something like this:
subplot(100, 1, 1:99) // plot your graph as you normally would
plot(...
subplot(100, 1, 100) // Plot a really small plot to get the axis
plot(...)
b = axis()
axis([b(1:2), 0, 0]) // set the y axis to really small
This is untested, you might need to fiddle around a little but it should hopefully put you on the right track.
I'm using the MATLAB plot feature to compare two vectors. I would like my X axis to represent 1 through 7, and then 14, 21, and then a category at the end for points with undetermined X values..(I'm also not sure how to represent these numberless point (they have Y values, just no X values) I could assign a large number outside any of my X values (1000) to these points, do the 1-7,14,21,1000 and then change the 1000 label to my 'string for un-numbered points'. ??
Here is a way to do it based on the example by The Mathworks here.
The trick is to create 2 x axis with different ranges and make one of them transparent. You can then play around with its properties. I modified a bit their code but kept most of their comments because they explain well the steps.
For the demo I used scatter to represent the points and colored the "good" points in red and the other point (here only 1) in green. You can customize all this of course. For instance I used a value of 100 and not 1000 for the x value of the 2nd axes, but I'll let you figure out how to modify it all to change the output as you wish.
clear
clc
close all
%// Create axes 1 and get its position
hAxes1 = axes;
axes_position = get(hAxes1, 'Position');
%// Create axes 2 and place it at the same position than axes 1
hAxes2 = axes('Position', axes_position);
%// Your data go here.
x = [1 7 14 21 100];
y = rand(1, length(x));
%// Plot the two sections of data on different axes objects
hPlot1 = scatter(hAxes1, x(1:4), y(1:4),40,'r','filled');
hold on
hPlot2 = scatter(hAxes2, x(end), y(end),40,'g','filled');
%// Link the y axis limits and fontsize property of the axes objects
linkaxes([hAxes1 hAxes2], 'y');
linkprop([hAxes1 hAxes2], 'FontSize');
%// Set the x range limits and tick mark positions of the first axes object
set(hAxes1, 'XLim', [1 25], ...
'XTick', [1 7 14 21])
%// Set the x range limits and tick mark positions for the second axes object.
%// Also set the background color to 'none', which makes the background
%// transparent.Add the label for the "super points".
set(hAxes2, 'Color', 'none', ...
'YTickLabel', [], ...
'XLim', [95 100], ...
'XTick', 100,'XTickLabel',{'Super Points'})
And the output:
EDIT
If you wish to add a fit line, I suggest adding a 3rd axes at the same position than the other 2, make it transparent and remove its X- and Y-ticks.
i.e. Add something like this:
hAxes3 = axes('Position', axes_position,'Color','none','YTick',[],'XTick',[]);
And in the call to polyfit/polyval, in my example you want to get only the first 4 elements (i.e. the red ones).
Hence:
p = polyfit(x(1:4),y(1:4),1);
y_poly = polyval(p,x(1:4));
And then plot the line on hAxes3:
hPlot3 = plot(x(1:4),y_poly)
Output:
I have a 3D mesh like in this picture.
Now what I want to do is create a plane that will intersect the surface at a certain Z value. I would then want to get the x and y coordinates of this intersection and have matlab output them.
What I'm planning on doing is that this picture is a model of a lake. This lake will have water evaporating that will be removing a certain z value of water. I would then like to see what the new shoreline would look like by obtaining the x and y coordinates of this intersection.
This is my code for plotting that picture.
function plot(x,y,z)
Contour = xlsread('C:\Users\Joel\Copy\Contour','A2:D4757');
x = Contour(:,1);
y = Contour(:, 2);
z = Contour(:,3);
F = TriScatteredInterp(x,y,z);
[X,Y]=meshgrid(linspace(-600,600,300));
Z=F(X,Y);
surf(X,Y,Z);
end
You can do this by simply thresholding the interpolated Z values
inside = Z < seaLevel; % binary mask of points inside water
shoreline = bwmorph( inside, 'remove' ); % a mask with only shoreline pixels eq to 1
figure;
surf( X, Y, Z, 'EdgeColor', 'none', 'FaceColor', [210,180,140]/255, 'FaceAlpha', .5 );
hold on;
ii = find( shoreline );
plot3( X(ii), Y(ii), seaLevel*ones(size(ii)), 'b', 'LineWidth', 2 );
The contour3 will give nicer boundaries:
[h,c]=contour3(X,Y,Z,[seaLevel seaLevel]);
seaLevel is given twice: otherwise contour3 thinks seaLevel is the number of levels to automatically calibrate. And to nicely annotate with the numeric height of your seaLevel:
clabel(h,c);
you may modify c to print "sea level" instead of num2str(seaLevel).
If you don't have the MATLAB toolbox for image processing you can't use the function "bwmorph". As a solution you can replace line 2 of Shai's code with the following code which reimplements the bwmorph function for parameter 'remove'. (The reimplementation is probably neither very perfomrant nor an exact reimplementatin (the borders of the matrix aren't used) - but the solution should work as a first step. Feel free to improve).
shoreline= zeros(size(inside));
for i_row = 2:size(inside,1)-1
for i_col = 2:size(inside,2)-1
if(inside(i_row,i_col))
if (~( inside(i_row+1,i_col) && ...
inside(i_row-1,i_col) && ...
inside(i_row,i_col+1) && ...
inside(i_row,i_col-1)))
inside2(i_row,i_col) = 1;
end
end
end
end
This is actually very basic and I've done it before (a long tme ago) but I can't find it now; I have a vector of data points that I want to plot with a line plot; however I want the lines to be horizontal and jump between each point so that it basically looks like a histogram. I thought I could just use plot() with a certain linespec, but I can't find one that fits. Ideas?
I believe the function you are looking for is stairs:
x = linspace(-2*pi,2*pi,40);
stairs(x,sin(x))
Let x and y be two vectors of the same size to be plotted using plot(x,y). How about
yy = reshape( [y(:) y(:)]', 1, [] );
yy(end) = []; % discard last element
xx = reshape( [x(:) x(:)]', 1, [] );
xx(1) = []; % discard first element
plot( xx, yy );
title('does this do the trick for you?');
I have a 2 column matrix(called M, which I visualize as two vectors using Matlab's plot command(plot(M)). I have two issues:
I want to label the vectors themselves on the plot.
I want to label each row of the matrix(i.e. each vector component) on the plot.
How would I go about doing those things?
An example:
M = cumsum(rand(10,2) - 0.5);
x = 1:size(M,1);
plot(x, M(:,1), 'b.-', x, M(:,2), 'g.-')
legend('M1', 'M2')
for i=x
text(i+0.1, M(i,1), sprintf('%.2f', M(i,1)), 'FontSize',7, 'Color','b');
text(i+0.1, M(i,2), sprintf('%.2f', M(i,2)), 'FontSize',7, 'Color','g');
end
Alternatively, you can use:
datacursormode()
which will enable the user to just point and click on points to see the data labels.
You may need to tweak this to get the positions of the labels exactly how you want them, but something like this will do the trick.
M = [1 2; 3 4; 5 6]
plot(M)
nrows = size(M, 1);
ncols = size(M, 2);
x = repmat(nrows - .3, 1, ncols);
y = M(end, :) - .3;
labels = cellstr([repmat('Col', ncols, 1), num2str((1:ncols)')]);
text(x, y, labels)
You can label each axis with the function:
xlabel('label')
ylabel('label')
These can also take cell arguments, where each row is a new line. That's handy for showing units. Labeling each point on the figure can be done as so:
for i=1:length(M)
text(M(i,1),M(i,2),'Label Text')
end
The label text can also be a string variable that you can edit with sprintf and make special strings for each point.