Drawing lines by dragging the mouse in matlab - matlab

I want to draw a set of disconnected lines on top of an image by dragging the mouse while pressing the left button. However, if I click on a previously drawn line to specify the starting point of the next line, the callback function is not being called and I don't get the point. Here is my code:
function main_test
S.fH = figure('menubar','none');
im = imread( 'image.jpg' );
S.aH = axes;
S.iH = imshow( im ); hold on
axis image;
X = [];
Y = [];
set(S.aH,'ButtonDownFcn',#startDragFcn)
set(S.iH,'ButtonDownFcn',#startDragFcn)
set(S.fH, 'WindowButtonUpFcn', #stopDragFcn);
function startDragFcn(varargin)
set( S.fH, 'WindowButtonMotionFcn', #draggingFcn );
pt = get(S.aH, 'CurrentPoint');
x = pt(1,1);
y = pt(1,2);
X = x;
Y = y;
end
function draggingFcn(varargin)
pt = get(S.aH, 'CurrentPoint');
x = pt(1,1);
y = pt(1,2);
X = [X x];
Y = [Y y];
plot(X, Y, 'r', 'LineWidth', 6);
hold on
drawnow
end
function stopDragFcn(varargin)
set(S.fH, 'WindowButtonMotionFcn', ''); %eliminate fcn on release
end
end
Would you please help me to identify the problem in this.
Thank you in a advance..
cheers,
Sawsan


You need to set the ButtonDownFcn property on the plotted line as well, i.e.
plot(X,Y,'r','LineWidth',6,'ButtonDownFcn',#startDragFcn)

Related

connect points during multiple Matlab plot calls

I would like to connect two or multiple data points during multiple Matlab plot calls. Below is some dummy code that shows what I am trying to accomplish,
function main()
close all
t = 0;
while t<10
x = rand(1,1);
y = rand(1,1);
t = t+1;
calculateErrorAndPlot(1,x,y,t)
end
return
function calculateErrorAndPlot(figureNumber,x,y,time)
figure(figureNumber);
if ~ishold
hold on
end
error = x-y;
plot(time,error,'.b');
return
Right now, I have to use '.b' to at least see the data points being plotted. Note that plot is being called with scalars.

You could update the XData and YData properties of a line already plotted to add a new point. For example:
function main
fig = figure;
ax = axes( 'Parent', fig );
line = plot( NaN, NaN, 'Parent', ax );
for t = 0:9
x = rand( 1, 1 );
y = rand( 1, 1 );
calculateErrorAndPlot( line, x, y, t )
end
end
function calculateErrorAndPlot( line, x, y, t )
xData = get( line, 'XData' );
yData = get( line, 'YData' );
xData(end+1) = t;
yData(end+1) = x - y;
set( line, 'XData', xData, 'YData', yData );
end

I would rewrite this, and remove the function:
time = [1:10];
for ii = 1:length(time)
x = rand(1,1);
y = rand(1,1);
error(ii) = x-y;
end
plot(time,error,'.-b')

Here is some code that works. However, I am open to suggestions or other code that may be simpler and/or faster :)
function calculateErrorAndPlot(figureNumber,x,y,time)
figure(figureNumber);
if ~ishold
hold on
end
error = x-y;
h = findobj(figure(figureNumber),'Type','line');
if isempty(h)
xx = time;
yy = error;
else
xx = [h(1).XData(end) time];
yy = [h(1).YData(end) error];
end
plot(xx,yy,'.-black');
return

How to manage the legend for many plots

How do I handle this issue
clear all; close all; clc;
r = 0:5;
zeta = 0:0.1:1;
for i = 1:size(zeta(:))
for j = 1:size(r(:))
X(i,j) = sqrt((1+(2*zeta(i)*r(j))^2)/((1-r(j)^2)^2+ (2*zeta(i)*r(j))^2));
end
plot(r,X);
xlabel('r = \omega/\omega_n');
ylabel('M = \frac{X}{Y}');
hold all
grid
[~,~,~,current_entries] = legend;
legend([current_entries {sprintf('\zeta = %i',zeta(i))}]);
end
figure
plot(r,X)
grid
The hold all command doesn't seem to be working properly. What can I do to fix this?

You will want to set the DisplayName property of the plot. Then when you create the legend, the labels will automatically be populated.
plot(r, X, 'DisplayName', 'name')
Also, the string that you were passing to sprintf for your legends needs to be escaped becuase sprintf thinks that \z is a control character.
plot(r, X, 'DisplayName', sprintf('\\zeta = %0.1f',zeta(k)))
Also, hold on is recommended over hold all. Also, it is best practice to specify the axes handle when calling hold to ensure that it is applied to the current axes.
hold(hax, 'on')
So if we incorporate these changes into your plotting code (along with #R.Falque's idea to use semilogy)
r = 0:0.001:5;
zeta = 0:0.1:1;
hax = axes();
colors = hsv(numel(zeta));
for k = 1:numel(zeta)
X = sqrt((1 + (2 * zeta(k) * r).^2) ./ ((1-r.^2).^2+ (2*zeta(k)*r).^2));
semilogy(r, X, ...
'DisplayName', sprintf('\\zeta = %0.1f',zeta(k)), ...
'Color', colors(k,:));
hold(hax, 'on')
end
grid(hax, 'on')
xlabel(hax, 'r = \omega/\omega_n', 'Interpreter', 'tex');
ylabel(hax, 'M = $\displaystyle\frac{X}{Y}$', 'Interpreter', 'latex');
L = legend('show');

You can also use cells array as follow:
clear all; close all; clc;
r = 0:0.001:5;
zeta = 0:0.1:1;
figure;
for i = 1:length(zeta)
for j = 1:length(r)
X(j) = sqrt((1+(2*zeta(i)*r(j))^2)/((1-r(j)^2)^2+ (2*zeta(i)*r(j))^2));
end
semilogy(r,X);
hold on
legend_string{i} = ['\zeta = ', num2str(zeta(i))];
end
hold off
grid
xlabel('r = \omega/\omega_n');
ylabel('M = $\frac{X}{Y}$','Interpreter', 'Latex');
legend(legend_string);
Note that you have an error in the X definition (corrected from X(i,j) to X(j)).

Draw tangent line on curve with MatLab

Can some one help me to find a tangent for a curve.
I have two data set (time, temp). Now I first fit this data using logarithmic function and now I want to draw a tangent over mouse click. I upload a code which is useful but I am not aware how to modify this. Thanks for help.
function test
hh = figure(1); clf, hold on
grid on
x = 0:0.01:2*pi;
f = #(x) sin(x);
fprime = #(x) cos(x);
plot(x, f(x), 'r')
axis tight
D = [];
L = [];
set(hh, ...
'WindowButtonMotionFcn', #mouseMove,...
'WindowButtonDownFcn', #mouseClick);
function mouseMove(varargin)
coords = get(gca, 'currentpoint');
xC = coords(1);
if ishandle(D)
delete(D); end
D = plot(xC, f(xC), 'ko');
end
function mouseClick(obj, varargin)
switch get(obj, 'selectiontype')
% actions for left mouse button
case 'normal'
coords = get(gca, 'currentpoint');
xC = coords(1);
yC = f(xC);
a = fprime(xC);
b = yC-a*xC;
if ishandle(L)
delete(L); end
L = line([0; 2*pi], [b; a*2*pi+b]);
case 'alt'
% actions for right mouse button
case 'extend'
% actions for middle mouse button
case 'open'
% actions for double click
otherwise
% actions for some other X-mouse-whatever button
end
end
end

MATLAB - How to make multiple markers moving simultaneous in 3d plot in MATLAB

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)

Matlab code to draw a tangent to a curve

I need to draw a tangent to a curve at a particular point (say the point is chosen by the user). I have written a code that allows the user to manually pick up two points and then a line is drawn between them. But I would like to automate the process. Can someone please suggest any algorithms/already implemented matlab codes to do so?

Try the function below. Of course, it needs lots of tweaking to apply to your case, but I think this is roughtly what you want.
function test
hh = figure(1); clf, hold on
grid on
x = 0:0.01:2*pi;
f = #(x) sin(x);
fprime = #(x) cos(x);
plot(x, f(x), 'r')
axis tight
D = [];
L = [];
set(hh, ...
'WindowButtonMotionFcn', #mouseMove,...
'WindowButtonDownFcn', #mouseClick);
function mouseMove(varargin)
coords = get(gca, 'currentpoint');
xC = coords(1);
if ishandle(D)
delete(D); end
D = plot(xC, f(xC), 'ko');
end
function mouseClick(obj, varargin)
switch get(obj, 'selectiontype')
% actions for left mouse button
case 'normal'
coords = get(gca, 'currentpoint');
xC = coords(1);
yC = f(xC);
a = fprime(xC);
b = yC-a*xC;
if ishandle(L)
delete(L); end
L = line([0; 2*pi], [b; a*2*pi+b]);
case 'alt'
% actions for right mouse button
case 'extend'
% actions for middle mouse button
case 'open'
% actions for double click
otherwise
% actions for some other X-mouse-whatever button
end
end
end