I have to create some draggable points on an axes. However, this seems to be a very slow process, on my machine taking a bit more than a second when done like so:
x = rand(100,1);
y = rand(100,1);
tic;
for i = 1:100
h(i) = impoint(gca, x(i), y(i));
end
toc;
Any ideas on speed up would be highly appreciated.
The idea is simply to provide the user with the possibility to correct positions in a figure that have been previously calculated by Matlab, here exemplified by the random numbers.
You can use the the ginput cursor within a while loop to mark all points you want to edit. Afterwards just click outside the axes to leave the loop, move the points and accept with any key.
f = figure(1);
scatter(x,y);
ax = gca;
i = 1;
while 1
[u,v] = ginput(1);
if ~inpolygon(u,v,ax.XLim,ax.YLim); break; end;
[~, ind] = min(hypot(x-u,y-v));
h(i).handle = impoint(gca, x(ind), y(ind));
h(i).index = ind;
i = i + 1;
end
Depending on how you're updating your plot you can gain a general speedup by using functions like clf (clear figure) and cla (clear axes) instead of always opening a new figure window as explained in this answer are may useful.
Alternatively the following is a very rough idea of what I meant in the comments. It throws various errors and I don't have the time to debug it right now. But maybe it helps as a starting point.
1) Conventional plotting of data and activating of datacursormode
x = rand(100,1);
y = rand(100,1);
xlim([0 1]); ylim([0 1])
f = figure(1)
scatter(x,y)
datacursormode on
dcm = datacursormode(f);
set(dcm,'DisplayStyle','datatip','Enable','on','UpdateFcn',#customUpdateFunction)
2) Custom update function evaluating the chosen datatip and creating an impoint
function txt = customUpdateFunction(empt,event_obj)
pos = get(event_obj,'Position');
ax = get(event_obj.Target,'parent');
sc = get(ax,'children');
x = sc.XData;
y = sc.YData;
mask = x == pos(1) & y == pos(2);
x(mask) = NaN;
y(mask) = NaN;
set(sc, 'XData', x, 'YData', y);
set(datacursormode(gcf),'Enable','off')
impoint(ax, pos(1),pos(2));
delete(findall(ax,'Type','hggroup','HandleVisibility','off'));
txt = {};
It works for the, if you'd just want to move one point. Reactivating the datacursormode and setting a second point fails:
Maybe you can find the error.
Related
This is part of the code the makes the video:
k = 10000;
j = 1;
v = VideoWriter('myVideo.avi');
open(v)
while j < k
axis([0 5 0 1000]);
plot(0:dr:R, u_sol_matrix(:,j))
frame = getframe(gcf);
writeVideo(v,frame);
j = j + 50;
% pause(0.01)
end
close(v)
Now, given a matrix u_sol_matrix, where every column represents a solution for a PDE at a certain time point, I plot the solutions and the by the getframe command capture these plots and make a movie out of it.
The problem is that the axis keeps changing as the plot keeps adjusting to the solution. I want the axis to be constant. How do I get this to work? I have tried adding axis but this does not work apparently.
k = 10000;
j = 1;
v = VideoWriter('myVideo.avi');
open(v)
while j < k
fig = figure(); % Explicitly create figure
plot(0:dr:R, u_sol_matrix(:,j))
axis([0 5 0 1000]); % first plot, then change axis
frame = getframe(gcf);
writeVideo(v,frame);
close(fig) % close figure explicitly.
j = j + 50;
% pause(0.01)
end
close(v)
Flipping the figure creation and setting axis limits should do the trick. When you call axis without an open figure, MATLAB creates one, only to overwrite it if you don't call hold on, thus changing the limits to whatever the plot "needs" to fit.
Like Adriaan answered, you just have to flip the order of plotting and setting axis limits to make this work.
However, when creating animations, it is faster to first initialize a figure and the graphics objects (i.e. lines, scatter points, etc.), and later update the data in a loop.
k = 10000;
j = 1;
v = VideoWriter('myVideo.avi');
open(v)
% some test data
x = 10;
y = sin(1:k);
% init a figure and plot handles
fig = figure(1);
p = plot(x, y(1), 'o'); % create line object, and store the handle
axis([9 11 -1 1]) % axis limits for test data
% update data during animation
while j < k
p.XData = x; % update X and Y data properties of line object
p.YData = y(j);
frame = getframe(gcf);
writeVideo(v,frame);
j = j + 50;
pause(0.01)
end
close(v)
Since you don't have to create a new line primitive each loop iteration, this will save a lot of time. You only have to adjust the X and Y data properties of the already existing line, which has considerable less overhead.
i have a problem and i hope that i will find help there.
This is my example code. Its only part of my algorithm. For imagine, how the point are moving, during the equations, i need show contour of function with two variables and into the points. Becase i have more difficult function than parabolic function, so the equations are too long than i need. For this reason i move contour ploting before the loop. But i have problem. I need show countour always and points only for i-loop and my solution doesnt work. Please help me!
[R S] = meshgrid(-5:0.1:5, -5:0.1:5);
figure
contour(R, S, R.^2 + S.^2, 5);
axis([-5,5,-5,5])
axis square
hold on
for i=1:50
a = 0;
b = 1:2
B = repmat(b,5,1)
A = unifrnd(a,B)
x = A(1:5,1);
y = A(1:5,2);
scatter(x,y,'fill')
hold off
pause(0.5)
end
You should store the handle to your scatter plot and simply update the XData and YData properties of it rather than destroying the plot objects every time
[R S] = meshgrid(-5:0.1:5, -5:0.1:5);
figure
contour(R, S, R.^2 + S.^2, 5);
axis([-5,5,-5,5])
axis square
hold on
% Create a scatter plot and store the graphics handle so we can update later
hscatter = scatter(NaN, NaN, 'fill');
for i=1:50
a = 0;
b = 1:2
B = repmat(b,5,1)
A = unifrnd(a,B)
x = A(1:5,1);
y = A(1:5,2);
% Update the X and Y positions of the scatter plot
set(hscatter, 'XData', x, 'YData', y);
pause(0.5)
end
I have a matlab function that contain some constant parameter, I want to draw that function, on say same figure, using hold on (probably) while changing the value of that constant.
This my code:
close all
clear all
clc
m = 5;
x = 1:1:10;
y = m*x + 10;
h1 = figure;
plot(x,y)
m = 10;
figure(h1);
hold on
plot(x,y,': r')
When I tried using this code, I got two lines coincident on each others; and it looks matlab just used last value for the parameter m how can I make it use different values.
I found some stuff here, but doesn't fulfill my needs.
Any suggestions?
You need to recalculate y as well:
m = 5;
x = 1:1:10;
y = m*x + 10;
h1 = figure;
plot(x,y); hold on;
m = 10;
y = m*x + 10;
figure(h1);
plot(x,y,': r')
Or create an anonymous function:
x = 1:1:10;
f = #(m) m*x + 10;
%// and then:
h1 = figure;
plot(x,f(5) ); hold on;
plot(x,f(10),': r');
Currently, you're only updating m but you also have to calculate y again. This is why it plots exactly the same y (i.e. m is still 5) function when you issue the second plot.
You might want to use a simple for loop for that, like:
m = 5;
x = 1:1:10;
figure;
hold on;
for m=1:1:10
y = m*x + 10;
plot(x,y,': r')
end
In addition to the short answer - improving the plot..
%% Data Preparations
x = 1:10;
ms = 3; % number of different slopes
%% Graph Preparations
hold on;
% Prepare the string cell array
s = cell(1, ms);
% Handle storage
h = zeros(1, ms);
% Plot graphs
for m=1:ms
y = m*x + 10;
h(m)= plot(x,y,'Color',[1/m rand() rand()]);
s{m} = sprintf('Plot of y(m=%d)', m);
end
% Plot all or select the plots to include in the legend
ind = [ms:-1:1] .* ones(1,ms); % plot all
%ind = [ 1 3 4 ]; % plot selected
% Create legend for the selected plots
legend(h(ind), s{ind});
Additional advice: When working with MATLAB and you try to improve the performance of your code, you shoud try to avoid using for-loops since MATLAB is MATrix manipulation and that's what it can do best. Ones you've taken this philosophy in, you'll create the most beautiful code one-liners! ;)
This script is an adoption of Steve Lord's post.
I am currently working on a project simulating the movement of two spacecraft and a moon (Phobos) around Mars. A MATLAB tool called SPICE gives me an array with the x, y and z distances and I have used these to plot the orbit which works fine. Now I want to get markers for each of the spacecraft and Phobos to see when they flyby each other. I got the markers working but not at the same time, they run after each other. I found an example on youtube so it must be possible but he has not released the code how to do it (https://www.youtube.com/watch?v=nArR2P0o4r4).
This is the code I have:
a = position_MEX_Mars(1,:);
b = position_MEX_Mars(2,:);
c = position_MEX_Mars(3,:);
k = position_MAVEN_Mars(1,:);
l = position_MAVEN_Mars(2,:);
m = position_MAVEN_Mars(3,:);
x = position_Phobos_Mars(1,:);
y = position_Phobos_Mars(2,:);
z = position_Phobos_Mars(3,:);
ah = axes;
set(ah,'XLim',[min(x) max(x)],'YLim',[min(y) max(y)],...
'ZLim',[min(z) max(z)]);
plot3(0,0,0,'ro-',x,y,z,a,b,c,k,l,m);
grid on;
hold on;
hpoint = line('XData', 0,'YData', 0,'ZData', 0,'Color','black','Marker',...
'o','MarkerSize',10);
ht = hgtransform('parent',ah);
set(hpoint,'Parent',ht);
for i =2:length(x)
trans = makehgtform('translate',[x(i) y(i) z(i)]);
set(ht,'Matrix',trans);
pause(0.001);
end
This will run a nice animated plot of the trajectory of Phobos in time but only Phobos and not simultaneous with MEX and MAVEN (spacecraft from ESA and NASA).
I tried this but does not work:
a = position_MEX_Mars(1,:);
b = position_MEX_Mars(2,:);
c = position_MEX_Mars(3,:);
k = position_MAVEN_Mars(1,:);
l = position_MAVEN_Mars(2,:);
m = position_MAVEN_Mars(3,:);
x = position_Phobos_Mars(1,:);
y = position_Phobos_Mars(2,:);
z = position_Phobos_Mars(3,:);
ah = axes;
set(ah,'XLim',[min(x) max(x)],'YLim',[min(y) max(y)],...
'ZLim',[min(z) max(z)]);
plot3(0,0,0,'ro-',x,y,z,a,b,c,k,l,m);
grid on;
hold on;
hpoint = line('XData', 0,'YData', 0,'ZData', 0,'Color','black','Marker',...
'o','MarkerSize',10);
ht = hgtransform('parent',ah);
set(hpoint,'Parent',ht);
for i =2:length(x)
trans1 = makehgtform('translate',[x(i) y(i) z(i)]);
set(ht,'Matrix',trans1);
trans2 = makehgtform('translate',[a(i) b(i) c(i)]);
set(ht,'Matrix',trans2);
pause(0.001);
end
I also tried merging the arrays so that it plots them each one step after each other but that makes the animation not smooth and is not satisfying for the project.
a = position_MEX_Mars(1,:);
b = position_MEX_Mars(2,:);
c = position_MEX_Mars(3,:);
k = position_MAVEN_Mars(1,:);
l = position_MAVEN_Mars(2,:);
m = position_MAVEN_Mars(3,:);
x = position_Phobos_Mars(1,:);
y = position_Phobos_Mars(2,:);
z = position_Phobos_Mars(3,:);
tempx = [position_MEX_Mars(1,:); position_Phobos_Mars(1,:); position_MAVEN_Mars(1,:)];
xt = tempx(:);
tempy = [position_MEX_Mars(2,:); position_Phobos_Mars(2,:); position_MAVEN_Mars(2,:)];
yt = tempy(:);
tempz = [position_MEX_Mars(3,:); position_Phobos_Mars(3,:); position_MAVEN_Mars(3,:)];
zt = tempz(:);
ah = axes;
set(ah,'XLim',[min(x) max(x)],'YLim',[min(y) max(y)],...
'ZLim',[min(z) max(z)]);
plot3(0,0,0,'ro-',x,y,z,a,b,c,k,l,m);
grid on;
hold on;
hpoint = line('XData', 0,'YData', 0,'ZData', 0,'Color','black','Marker',...
'o','MarkerSize',10);
ht = hgtransform('parent',ah);
set(hpoint,'Parent',ht);
for i =2:length(x)
trans = makehgtform('translate',[xt(i) yt(i) zt(i)]);
set(ht,'Matrix',trans);
pause(0.001);
end
I think I am close but I seem to be missing something and my knowledge of MATLAB is not that great yet. I hope you can help me out.
Cheers Jeroen
Here's a simplified (and not physically correct) example that could perhaps be useful:
t = linspace(0,2,1000); %// time parameter
x1 = 10*cos(2*pi*t+1);
y1 = 5*sin(2*pi*t+1); %// trajectory of object 1
x2 = 2*cos(6*pi*t-2);
y2 = 3*sin(6*pi*t-2); %// trajectory of object 1
plot(x1,y1,'color',[.5 .5 .5]); %// plot trajectory of object 1
hold on
plot(x2,y2,'color',[.5 .5 .5]); %// plot trajectory of object 2
h1 = plot(x1(1),y1(1),'ro'); %// plot initial position of object 1
h2 = plot(x2(1),y2(1),'b*'); %// plot initial position of object 2
axis([-12 12 -12 12]) %// freeze axis size
grid on
for n = 1:numel(t)
set(h1, 'XData', x1(n), 'YData', y1(n)); %// update position of object 2
set(h2, 'XData', x2(n), 'YData', y2(n)); %// update position of object 2
drawnow %// refresh figure
end
The thing that you tries to do is not really as easy as you think. The main issue is that you need to update everything at the same time. This have been implemented in several ways during the years. One way to do this is by using a so called a double buffer.
This means that you have two "surfaces" to paint on. In matlab this is translated to 2 axes (or 2 figures maybe). However, you do only have one axes visible at the same time. This means that you will have time to paint everything on the "hidden surface" before displaying the content. When you are done with everything you need you just switch which surface being visible.
It is possible that this can be done in a simpler way, but I am not familiar with the hgtransfrom functions in matlab.
EDIT
This is an example how it can be done
function test()
fig = figure;
ax1 = axes;
plot(1:10);
ax2 = axes;
plot(1:10,'r');
setVisibility(ax2,'off');
pause(1);
for k = 1:5
setVisibility(ax2,'on');
setVisibility(ax1,'off');
pause(1);
setVisibility(ax1,'on');
setVisibility(ax2,'off');
pause(1);
end
function setVisibility(ax, visibility)
set(ax, 'visible', visibility)
set(findall(ax), 'visible', visibility)
I'd like to draw a curve on an empty (semilog-y) graph by clicking the points I want it to run through, on the X-Y plane.
Is there a function for this?
edit: I'm trying to do this by obtaining the position of last pointer click -
axis([0 3000 0 1000]);
co=get(gcf, 'CurrentPoint');
It seems to return the cursor position at the time of execution, but it does not change later.
edit2: Here's what works for me. The actual drawing I can do by using the arrays of points collected.
clear
clc
h=plot(0);
grid on;
xlim([0 3000]);
ylim([0 1000]);
datacursormode on;
% Enlarge figure to full screen.
screenSize = get(0,'ScreenSize');
set(gcf, 'units','pixels','outerposition', screenSize);
hold on;
% Print the x,y coordinates - will be in plot coordinates
x=zeros(1,10); y=zeros(1,10);
for p=1:10;
[x(p),y(p)] = ginput(1) ;
% Mark where they clicked with a cross.
plot(x(p),y(p), 'r+', 'MarkerSize', 20, 'LineWidth', 3);
% Print coordinates on the plot.
label = sprintf('(%.1f, %.1f)', x(p), y(p));
text(x(p)+20, y(p), label);
end
Not really, but now there is:
function topLevel
%// parameters
xrange = [0 100];
yrange = [1e-4 1e4];
%// initialize figure, plot
figure, clf, hold on
plot(NaN, NaN);
axis([xrange yrange]);
set(gca, 'YScale', 'log')
t = text(sum(xrange)/2, sum(yrange)/2, ...
'<< Need at least 3 points >>',...
'HorizontalAlignment', 'center');
%// Main loop
xs = []; p = [];
ys = []; P = [];
while true
%// Get new user-input, and collect all of them in a list
[x,y] = ginput(1);
xs = [xs; x]; %#ok<AGROW>
ys = [ys; y]; %#ok<AGROW>
%// Plot the selected points
if ishandle(p)
delete(p); end
p = plot(xs, ys, 'rx');
axis([xrange yrange]);
%// Fit curve through user-injected points
if numel(xs) >= 3
if ishandle(t)
delete(t); end
%// Get parameters of best-fit in a least-squares sense
[A,B,C] = fitExponential(xs,ys);
%// Plot the new curve
xp = linspace(xrange(1), xrange(end), 100);
yp = A + B*exp(C*xp);
if ishandle(P)
delete(P); end
P = plot(xp,yp, 'b');
end
end
%// Fit a model of the form y = A + B·exp(C·x) to data [x,y]
function [A, B, C] = fitExponential(x,y)
options = optimset(...
'maxfunevals', inf);
A = fminsearch(#lsq, 0, options);
[~,B,C] = lsq(A);
function [val, B,C] = lsq(A)
params = [ones(size(x(:))) x(:)] \ log(abs(y-A));
B = exp(params(1));
C = params(2);
val = sum((y - A - B*exp(C*x)).^2);
end
end
end
Note that as always, fitting an exponential curve can be tricky; the square of the difference between model and data is exponentially much greater for higher data values than for lower data values, so there will be a strong bias to fit the higher values better than the lower ones.
I just assumed a simple model and used a simple solution, but this gives a biased curve which might not be "optimal" in the sense that you need it to be. Any decent solution really depends on what you want specifically, and I'll leave that up to you ^_^