I am looking to create a simple log(x) graph within MATLAB in which the model shows the point moving along the curve with time.
The overall aim is to have two of these graphs alongside one another and to apply an algorithm to them. I am really unsure where to start here.
I am relatively new at MATLAB coding so any help would be very useful!
Thanks
Luke
Here is a variation on #Jacob's solution. Instead of redrawing everything at each frame (clf) we simply update the point's location:
%# control animation speed
DELAY = 0.01;
numPoints = 600;
%# create data
x = linspace(0,10,numPoints);
y = log(x);
%# plot graph
figure('DoubleBuffer','on') %# no flickering
plot(x,y, 'LineWidth',2), grid on
xlabel('x'), ylabel('y'), title('y = log(x)')
%# create moving point + coords text
hLine = line('XData',x(1), 'YData',y(1), 'Color','r', ...
'Marker','o', 'MarkerSize',6, 'LineWidth',2);
hTxt = text(x(1), y(1), sprintf('(%.3f,%.3f)',x(1),y(1)), ...
'Color',[0.2 0.2 0.2], 'FontSize',8, ...
'HorizontalAlignment','left', 'VerticalAlignment','top');
%# infinite loop
i = 1; %# index
while true
%# update point & text
set(hLine, 'XData',x(i), 'YData',y(i))
set(hTxt, 'Position',[x(i) y(i)], ...
'String',sprintf('(%.3f,%.3f)',[x(i) y(i)]))
drawnow %# force refresh
%#pause(DELAY) %# slow down animation
i = rem(i+1,numPoints)+1; %# circular increment
if ~ishandle(hLine), break; end %# in case you close the figure
end
A simple solution is:
x = 1:100;
y = log(x);
DELAY = 0.05;
for i = 1:numel(x)
clf;
plot(x,y);
hold on;
plot(x(i),y(i),'r*');
pause(DELAY);
end
You may want to have a look at the COMET function, which will make an animation of the curve.
For example (using the same numbers as #Jacob)
x = 1:100;
y = log(x);
comet(x,y)
If you want to show the point moving on the line (not 'drawing' it), you simply plot the line before
x = 1:100;
y = log(x);
plot(x,y,'r')
hold on %# to keep the previous plot
comet(x,y,0) %# 0 hides the green tail
a little more complex solution along the same lines as #Jacob. Here I add some optimization using handle graphics and a MATLAB movie object for playback.
x=1:100;
y=log(x);
figure
plot(x,y);
hold on; % hold on so that the figure is not cleared
h=plot(x(1),y(1),'r*'); % plot the first point
DELAY=.05;
for i=1:length(x)
set(h,'xdata',x(i),'ydata',y(i)); % move the point using set
% to change the cooridinates.
M(i)=getframe(gcf);
pause(DELAY)
end
%% Play the movie back
% create figure and axes for playback
figure
hh=axes;
set(hh,'units','normalized','pos',[0 0 1 1]);
axis off
movie(M) % play the movie created in the first part
solution can be this way
x = .01:.01:3;
comet(x,log(x))
Related
I'm trying to create an animated plot but my code is very slow, perhaps the method I'm using is too naive. In the below example, I have 4 subplots each with 3 lines, which I update in a 'time' loop.
clc;clear;close all;
state = {'$x-Position$','$x-Velocity$','$y-Position$','$y-Velocity$'};
ylabels = {'$x$','$\dot{x}$','$y$','$\dot{y}$'};
options1 = {'interpreter','latex'};
options2 = {'interpreter','latex','fontsize',20};
maxT = 300;
for pp = 1:4
hh1(pp)=subplot(2,2,pp);
xlabel('$t$',options2{:});
ylabel(ylabels{pp},options2{:});
title(state{pp},options1{:})
xlim([0 maxT])
hold on
end
x = randn(4,300);
z = randn(4,300);
x_est = randn(4,300);
for k = 2:maxT
for p = 1:4
plot(hh1(p),k-1:k,x(p,k-1:k),'b','linewidth',2)
plot(hh1(p),k-1:k,z(p,k-1:k),'m')
plot(hh1(p),k-1:k,x_est(p,k-1:k),':k','linewidth',2)
end
drawnow;
end
As can be seen from the profiler output, the drawnow is killing the time. Is there any way I can be more efficient in creating this animation?
Because you want an animation, there is no alternative to using drawnow to update the frame. However, it's not drawnow in particular which is slowing you down - the profiler can be misleading... drawnow simply updates all of the graphics changes since the last re-draw, which in your case is a dozen new plots!
You'll find that hold is pretty slowing. For instance if you're wiser about your holding, remove the existing hold on and only hold when actually plotting
% ... above code the same but without 'hold on'
for p = 1:4
hold(hh1(p), 'on');
% plots
hold(hh1(p), 'off');
end
This saves ~10% time on my PC (12.3sec down to 11.3sec).
The real speed up comes from removing hold entirely, along with all of the individual plot calls! This method also doesn't touch the line formatting which will help with speed. See a previous question about updating plot data here.
Simply update the plot data instead of adding plots. This gives me a speedup of ~68% (12.3sec down to 4.0sec).
% ... your same setup
% Initialise plot data
x = randn(4,300);
z = randn(4,300);
x_est = randn(4,300);
plts = cell(4,3);
hh1 = cell(4,1);
% Loop over subplots and initialise plot lines
for p = 1:4
hh1{p}=subplot(2,2,p);
xlabel('$t$',options2{:});
ylabel(ylabels{p},options2{:});
title(state{p},options1{:})
xlim([0 maxT])
% Hold on to make 3 plots. Create initial points and set line styles.
% Store the plots in a cell array for later reference.
hold on
plts{p,1} = plot(hh1{p},1:2,x(p,1:2),'b','linewidth',2);
plts{p,2} = plot(hh1{p},1:2,z(p,1:2),'m');
plts{p,3} = plot(hh1{p},1:2,x_est(p,1:2),':k','linewidth',2);
hold off
end
% March through time. No replotting required, just update XData and YData
for k = 2:maxT
for p = 1:4
set(plts{p,1}, 'XData', 1:k, 'YData', x(p,1:k) );
set(plts{p,2}, 'XData', 1:k, 'YData', z(p,1:k) );
set(plts{p,3}, 'XData', 1:k, 'YData', x_est(p,1:k) );
end
drawnow;
end
Now the plotting is pretty optimised. If you want the animation to be even quicker then just plot every 2nd, 3rd, ..., nth timestep instead of every timestep by using for k = 2:n:maxT.
I want to produce a animated gif of a solution to a partial differential equation. That is the gif should show the solution at specific time.
Currently I can only make pictures in which all times are plotted.
Below is my entire program, with figure(3) being my attempt of making a gif.
clear all;
close all;
%%%%%%%%%%%%
% For slide 27 of Diffusion 1D
% The equation to be graphed in latex form is
% u(x,t)=\frac{1}{L}+\frac{2}{L}\sum^{\infty}_{n=1}cos(\frac{n\pi x_0}{L})cos(\frac{n\pi x}{L})e^{-k(\frac{n\pi}{L})^2t}
%%%%%%%%%%%%
%define constants
%note that the constants listed in the file are arbitrary
L = 2; %length of the rod
k= 0.01; % Diffusivity, which is assume to be constant but can be a function of x
x0 = 1; %location of the inital condition i.e. f(x)=delta(x-x0)
tmax= 50; %maximum amount of time the simulation runs
nmax = 200; % maximum value for n, increase to accuracy
tgrid = 21; %The number of points to be evaluated in the time domain
xgrid = 51; %The number of points to be evaluated in the space domain
%initialize variables
u=zeros(tgrid,xgrid); %preallocate array used for storing values of the solution
t=linspace(0,tmax,tgrid);%We assume that time is evenly distributed
x=linspace(0,L,xgrid); %We assume that space is evenly distributed
%Plotting variables
figure(1);
hold on;
axis([0 L -inf inf]);
xlabel('x');
ylabel('u(x,t)');
%Calculation,
for i=1:tgrid
for j=1:xgrid
seriesSum=0;
%Calculate the fourier series up to nmax for each point u(x,t)
for n= 1:nmax
seriesSum= seriesSum + cos(n*pi*x0/L)*cos(n*pi*x(j)/L)*exp(-k*t(i)*(n*pi/L)^2);
end
%Finish calcuation for solution at a specific point
u(i,j)= 1/L+(2/L)*seriesSum;
end
%After we have calculated all points at time t, we graph it for time t
plot(x,u(i,:),'linewidth',4);
end
saveas(gcf,'PDE_sol.png')%Save figure as png in current directory
%run a second loop that does not include the initial condition to get a
%better view of the long term behaviour.
%Plotting variables
figure(2);
hold on;
axis([0 L -inf inf]);
xlabel('x');
ylabel('u(x,t)');
for i=2:tgrid
plot(x,u(i,:),'linewidth',4);
end
saveas(gcf,'PDE_sol_without_inital.png')%Save figure as png in current directory
%Create a gif verison of figure 2
figure(3);
axis([0 L -inf inf]);
xlabel('x');
ylabel('u(x,t)');
filename = 'PDE_sol.gif';
for i=2:tgrid
plot(x,u(i,:),'linewidth',4);
drawnow
frame = getframe(1);
im = frame2im(frame);
[imind,cm] = rgb2ind(im,256);
if i == 2;
imwrite(imind,cm,filename,'gif', 'Loopcount',inf);
else
imwrite(imind,cm,filename,'gif','WriteMode','append');
end
end
The output gif that I get is
which is clearly not animated.
Note: If you think there is a better place to post this question please direct me to it. As my issue is with the MATLAB programming language and not the math involved I thought this would be the best place to post my question.
The first input to getframe is the handle of the figure that you'd like to take a screenshot of. As you have it written, you are grabbing figure 1 which is actually referring to the first figure that you create that you aren't updating within your loop.
You have assigned a numeric handle of 3 to the figure that you create right before your last loop so you'll want to tell getframe to use that figure instead.
Additionally, I would create one plot object and update the XData and YData rather than continuously creating new plot objects. The issue with calling plot continuously is that it's slow AND it completely resets all of your axes settings such as x and y labels as well as x and y limits.
% Store the handle to the figure in hfig
hfig = figure(3);
% Create the initial plot object
hplot = plot(NaN, NaN, 'LineWidth', 4);
axis([0 L 0 2]);
xlabel('x');
ylabel('u(x,t)');
filename = 'PDE_sol.gif';
for i=2:tgrid
% Update the plot appearance
set(hplot, 'XData', x, 'YData', u(i,:));
drawnow
% Get a screenshot of THIS figure
frame = getframe(hfig);
im = frame2im(frame);
[imind,cm] = rgb2ind(im,256);
if i == 2;
imwrite(imind,cm,filename,'gif', 'Loopcount',inf);
else
imwrite(imind,cm,filename,'gif','WriteMode','append');
end
end
I have used the code provided by #Amro in other question:
%# control animation speed
DELAY = 0.01;
numPoints = 600;
%# create data
x = linspace(0,10,numPoints);
y = log(x);
%# plot graph
figure('DoubleBuffer','on') %# no flickering
plot(x,y, 'LineWidth',2), grid on
xlabel('x'), ylabel('y'), title('y = log(x)')
%# create moving point + coords text
hLine = line('XData',x(1), 'YData',y(1), 'Color','r', ...
'Marker','o', 'MarkerSize',6, 'LineWidth',2);
hTxt = text(x(1), y(1), sprintf('(%.3f,%.3f)',x(1),y(1)), ...
'Color',[0.2 0.2 0.2], 'FontSize',8, ...
'HorizontalAlignment','left', 'VerticalAlignment','top');
%# infinite loop
i = 1; %# index
while true
%# update point & text
set(hLine, 'XData',x(i), 'YData',y(i))
set(hTxt, 'Position',[x(i) y(i)], ...
'String',sprintf('(%.3f,%.3f)',[x(i) y(i)]))
drawnow %# force refresh
%#pause(DELAY) %# slow down animation
i = rem(i+1,numPoints)+1; %# circular increment
if ~ishandle(hLine), break; end %# in case you close the figure
end
but I need to change the velocity of the marker. I've tried changing the value of DELAY, but it didn't work. The point is that I can't change the numPoints (size of the function), so I don't know hot to do it.
Any ideas?
Thanks!
Just uncomment the pause(DELAY) in the infinite loop. Change DELAY to a suitable value
That's how I draw two graphics (thanks for guys who helped me to do that):
clear
logsFolder = 'C:\logs\';
stocks = {'log'};
for stock = stocks
filename = [logsFolder stock{1} '.log'];
fLog = fopen(filename);
data = textscan(fLog, '%f:%f:%f:%f %f %f %f');
fclose(fLog);
% hh:min:sec:millisec
secvec = [60*60 60 1 1e-3];
x = [data{1:4}] * secvec';
y = data{5};
yPrice = data{6};
xindays = x / (24*60*60);
figure;
[AX,H1,H2] = plotyy(xindays,y,xindays,yPrice);
set(AX(1),'xtick',[]);
lo1 = min(y);
hi1 = max(y);
lo2 = min(yPrice);
hi2 = max(yPrice);
if (hi2/lo2 > hi1/lo1)
ylim(AX(1),[lo1 hi2/lo2 * lo1]);
ylim(AX(2),[lo2 hi2]);
else
ylim(AX(1),[lo1 hi1]);
ylim(AX(2),[lo2 hi1/lo1 * lo2]);
end
ticklabelformat(AX(2),'y','%g')
ticklabelformat(AX(2),'x',{#tick2datestr,'x','HH:MM:SS'})
title(stock);
% iNeedToDrawThat = data{7}
end
Input file example is available here As you can see my file contains the last column which I also want to display. The range should be from 0 (at the bottom of figure) to the maximum value (at the up of the graph). So I need to draw three graphics somehow. It's ok to omit axis with labels for the third graph as I already have two axis and I have no place to add third one. However it's ok to "overlap" two axis if possible.
I have no idea how to do that so I'm looking for your help.
I've tried that but it doesn't work:
figure;
[AX,H1,H2] = plotyy(xindays,y,xindays,yPrice);
hold on;
volume = data{7};
plot(xindays, volume);
hold off;
I have already mentioned a similar question in the comments, it should give you plenty of ideas...
Anyway, I've put together a solution to plot multiple y axes. Right now the code is a bit involved, but it should be possible to refactor a re-usable function out of it (like the addaxis function on the File Exchange).
The idea is to first plot each curve in a separate axis (all superimposed), and make them transparent (except the bottom one). Next we create copies of this set of axes and shift them along the x-direction. We also make those copies transparent, but now we can show the tick-marks along the y-axis of each. Finally we give them correct z-order, and link the x and y limits so that we can use the pan and zoom functionality.
%# read and parse data from file
fid = fopen('log.log','rt');
C = textscan(fid, '%s %f %f %f', 'CollectOutput',true);
fclose(fid);
dt = datenum(C{1}, 'HH:MM:SS:FFF');
data = C{2};
NUM = size(data,2);
%# create a wider figure
hFig = figure('Position',get(0,'DefaultFigurePosition').*[1 1 1.7 1]);
%# some properties
clr = lines(NUM);
bgClr = get(0,'DefaultFigureColor');
pos = get(0,'DefaultAxesPosition');
pp = 0.1; % shift in normalized units: pos(1)
%# create plot axes (make axis invisible)
hAx = zeros(NUM,1);
for i=1:NUM
hAx(i) = axes('Parent',hFig, 'Color','none', ...
'XColor',bgClr, 'YColor',bgClr, ...
'Units','normalized', 'Position',pos+[(NUM-1)*pp 0 -(NUM-1)*pp 0]);
line(dt, data(:,i), 'Color',clr(i,:), 'Parent',hAx(i))
end
axis(hAx, 'tight') %# tight x/y limits
%# create shifted copies of axes to show y-ticks
hAxx = zeros(size(hAx));
for i=1:NUM
hAxx(i) = copyobj(hAx(i), hFig);
delete(get(hAxx(i),'Children')); %# keep only axis
set(hAxx(i), 'YColor',clr(i,:), ...
'Units','normalized', 'Position',pos+[(NUM-i)*pp 0 -(NUM-i)*pp 0]);
ylabel(hAxx(i), sprintf('Axis %d',i))
end
xlabel(hAxx(1), 'datetime')
title(hAxx(1), 'Log')
datetick(hAxx(1), 'x', 'HH:MM', 'keeplimits')
%# set 1st axis copy as current axis
set(hFig, 'CurrentAxes',hAxx(1))
%# adjust ticks of axes
set(hAx(1), 'Color','w') %# give white bg to 1st axis
set(hAxx(1), 'XColor','k') %# show xticks of 1st axis copy
set(hAxx(2:end), 'XTick',[], 'XTickLabel',[])
set(hAx, 'XTick',[], 'XTickLabel',[], 'YTick',[], 'YTickLabel',[])
%# fix z-order
for i=3:-1:1, uistack(hAxx(i),'top'), end
uistack(hAx(1), 'bottom')
%# link x/y limits so that panning/zooming works
lh = cell(NUM+1,1);
for i=1:NUM
lh{i} = linkprop([hAxx(i);hAx(i)], 'YLim');
end
lh{end} = linkprop([hAxx;hAx], 'XLim');
The result:
The panning/zooming is a bit funny, you have to initiate them by starting to drag from the side (the shifted colored axes). This is because the first one (corresponding to the blue line) is the one on top, thus catches all mouse clicks.
Note: I see you are using a custom function ticklabelformat, which I haven't tested in combination with the above code. I will leave that part to you..
HTH
sample use of hold on
figure;
plot(x1,y1);
hold on
plot(x2,y2);
plot(x3,y3);
hold off
do "figure" and "hold on" only once outside the loop. then plot all the graphs you need
figure;
[AX,H1,H2] = plotyy(xindays,y,xindays,yPrice);
hold on;
volume = data{7};
plot(xindays, volume);
hold off;
if you do it the way you suggested using hold on, i.e. use plotyy() first then the axes won't adjust so if you 3rd series is out of the range of your first set of axes then it won't appear. Try just flipping them and see if that produces a result?
volume = data{7};
plot(xindays, volume);
hold on;
[AX,H1,H2] = plotyy(xindays,y,xindays,yPrice);
This way the axes should adjust
For example:
t = 1:10;
x = t*2;
y = t*-2;
z = x + 1000;
Now compare
plot(t,z, 'r')
hold on
plotyy(t,x, t,y)
to
plotyy(t,x, t,y)
hold on
plot(t,z, 'r')
I'm trying to animate the graph of a function but I cant get the program to graph the correct points. I want to plot points between time 0 and 10 and animate this graph. How do I get the plot as a function of time?
clear;
w = 2*pi;
t = 0:.01:10;
y = sin(w*t);
x = cos(w*t);
for j=1:10
plot(x(6*j),y(6*j),'*');
axis square;
grid on;
F(j) = getframe;
end
movie(F,1,1);
I refined the code to:
clear;
w = 2*pi;
for j=2:11
t=j-1;
y = sin(w*t);
x = cos(w*t);
plot(x(t),y(t),'*');
axis square;
grid on;
F(j) = getframe;
end
movie(F);
This should do what I'm trying however now I'm getting an "Index exceeds matrix dimension." How can I solve this?
Here is an example that show an animated point along a circular path, while recording an AVI movie.
To learn more about doing animations and recording movies in MATLAB, check out this guide.
%# some parameters
ERASEMODE = 'normal'; %# normal,xor
RENDERER = 'painters'; %# painters,zbuffer,opengl
%# data
t = linspace(0,2*pi,100)'; %'# adjust number of points here
D = [cos(t) -sin(t)];
%# plot circluar path
figure('DoubleBuffer','on', 'Renderer',RENDERER)
plot(D(:,1), D(:,2), 'Color','b', 'LineWidth',2)
grid on, axis([-1.5 1.5 -1.5 1.5]), axis square
xlabel('x'), ylabel('y'), title('Circle Animation')
%#set(gca, 'DrawMode','fast')
%# moving point
hPoint = line('XData',D(1,1), 'YData',D(1,2), 'EraseMode',ERASEMODE, ...
'Color','r', 'Marker','.', 'MarkerSize',30);
%# moving coordinates text
hTxtCoords = text(D(1,1), D(1,2), sprintf('(%.2f,%.2f)',D(1,:)), ...
'Color',[0.2 0.2 0.2], 'FontSize',8, 'EraseMode',ERASEMODE, ...
'HorizontalAlignment','left', 'VerticalAlignment','top');
%# angle text
hTxtAngle = text(0, 0, num2str(t(1),'%.02f'), ...
'FontSize',15, 'EraseMode',ERASEMODE, ...
'HorizontalAlignment','center', 'VerticalAlignment','middle');
%# prepare video output
useVideoWriter = ~verLessThan('matlab','7.11');
if useVideoWriter
vid = VideoWriter('vid.avi');
vidObj.Quality = 100;
vid.FrameRate = 30;
open(vid);
else
vid = avifile('vid.avi', 'fps',30, 'quality',100);
end
%# loop
for i=1:numel(t)
set(hPoint, 'XData',D(i,1), 'YData',D(i,2)) %# update point location
set(hTxtAngle, 'String',num2str(t(i),'%.02f')) %# update angle text
set(hTxtCoords, 'Position',D(i,:), ... %# update angle text
'String',sprintf('(%.3f,%.3f)',D(i,:)))
drawnow %# force refresh
if ~ishandle(hPoint), break; end %# if you close the figure
%# capture frame
if useVideoWriter
writeVideo(vid,getframe);
else
vid = addframe(vid, getframe(gcf));
end
end
%# close and save video output
if useVideoWriter
close(vid);
else
vid = close(vid);
end
%# open AVI file using system default player
winopen('vid.avi')
It's doing exactly what you ask it to do. You're subsampling the x and y, so it looks kind of funny.
Try
plot(x,y);
axis square;
ax = axis;
for jx = 1 : length(t),
plot(x(ix), y(ix), '*');
axis(ax); grid on;
F(ix) = getframe;
end
movie(F, 1, 1/(t(2)-t(1)))
I would also use t = 1 : 0.1 : 10; so that it plots at 10 FPS instead of 100. Slowing the frequency down to, say, w = pi; will be smoother as well.
At the end of the day, Matlab is just not a great animation solution.
Answer to refined code question
You'd need to use plot(x,y);, but this will reveal another error - your frame index does not start at 1. It will choke on F(j) in the first iteration, where j = 2. Why not just loop over t = 1 : 10?