I'm trying to plot a circle in a function using viscircles, and then come back to that function later on to plot another circle like the figure shown below:
At the moment, I can only plot single circles using these lines of code:
figure
center = [numberX numberY];
xlim([-0.1 10.1])
ylim([-0.1 10.1])
axis square
artwork = viscircles(center,size,'Color',colorControl)
After plotting the first viscircles, control rolls back over to a prompts function to get data for the next viscircles, but when it comes back around to plotting, the original viscircles is overwritten, even when I tried using hold on. Any advice would be much appreciated.
viscircles by default will flush the figure and draw only the circles specified by the inputs you provide it so hold on will not work.
What you can do instead is keep appending to your data so that the original data is displayed followed by a new circle each time you prompt for new data.
As such, do something like this. Assuming that you have a function called getNewCenter that returns a new center, the size of the circle and the colour, and matrices that contain the centers to display as well as their sizes:
centers = [];
sizes = []; % Matrices that contain the centers and sizes
while true % Keep iterating...
[numberX, numberY, size, colorControl] = getNewCenter; % Get new center, size and colour
% Add to the data
centers = [centers; numberX numberY];
sizes = [sizes; size];
% Plot the circles
xlim([-0.1 10.1]);
ylim([-0.1 10.1]);
axis square;
artwork = viscircles(centers, sizes, 'Color', colorControl);
end
Related
I use the tiledlayout(2,2) command to create a plot in Matlab. The first three title fields filled with normal plots. The fourth and last field is a field with an image. I used the commands IMG = 'mypic.tif'and imshow(IMG).I wonder why I can not change the size of my image. Is this not possible with the tiledlayoutcommand? I have looked up the documentary for tiledlayout and imshow(), but found nothing which helps me.
It indeed seems as if this is not possible using the tiledlayout functionality. However, it is possible using the subplot functionality. Below, I will give an example how this works.
Consider the following script:
% Generate some dummy data for the four plots
x = linspace(0, 2*pi, 25);
y = sin(x);
% Load sample image
image = imread('ngc6543a.jpg');
% Generate the figure
fig = figure(1);
% The three subplots
for i = 1:3
subplot(2,2,i);
plot(x, y);
end
% The image
subplot(2,2,4);
imshow(image);
% Increase size of the image
size_factor = 1.4; % 1.0 is original size
im_ax = fig.Children(1); % axes belonging to image
dims = im_ax.Position(3:4); % current dimensions
dims_new = size_factor * dims; % scale old dimensions
dxdy = (dims_new - dims) / 2; % offset for left bottom corner of image
im_ax.Position = [im_ax.Position(1:2) - dxdy, dims_new]; % update position
In this script, we start by generating some dummy data for the three 'normal' plots and loading a sample image (this image came with my MATLAB installation). Subsequently, we create a figure. After the figure has been created, I add the three dummy plots to the figure using a for loop and the subplot functionality. Then, we plot the image using imshow in the fourth subplot.
Now, the interesting part begins. First of all, I define a scale factor for the image (size_factor). Then, I retrieve the axes in which the image is plotted and store it in im_ax. From this axes, I retrieve the last two elements of the Position field and store them in dims. These two elements define the size of the axes. Based on the value of size_factor, I calculate the new size of the axes and store this in dims_new. To ensure that the axes (and thus the image) remains centered, we need to calculate by how much we need to shift the left bottom corner of the axes (whose coordinates are stored in the first two elements of the Position field). This result is stored in dxdy. The last thing we do is simply updating the Position field of the axes in which the image is plotted.
Now, to show you some results:
size_factor equals 1.0:
size_factor equals 1.4:
size_factor equals 0.55:
I have a scatterplot of data in Matlab, along with a horizontal linegraph which divides two sub groups of this data - all on the same plot. I have plotted these two entities separately using the hold on command.
Ideally, I want the plot window to automatically adjust to just the scatterplot data, and would prefer the horizontal line I plotted to simply extend off the screen in all cases. Is there a simple way to do this?
At the moment when I change the limits of the horizontal line, the graph window shifts to accommodate these points, skewing the view of the scatterplot data I'm actually interested in.
Example:
% central line segment
boundary_line = plot(csv_results.data(:,9),csv_results.data(:,10));
% negative extension of line segment off screen
line_negext = plot([-10,csv_results.data(1,9)],[csv_results.data(1,10),csv_results.data(1,10)]);
% positive extension of line segment off screen
line_posext = plot([10,csv_results.data(6,9)],[csv_results.data(6,10),csv_results.data(6,10)]);
% scatterplot data of interest
scatt_data = plot(csv_results.data(:,3),csv_results.data(:,4));
UPDATE: My problem is that, as seen in my code above, I need to plot two line segments at different y values that continue to positive and negative infinity, which link up to an existing plot in the middle. If I use yline I can simply draw one horizontal line - if I use xlim I risk cropping out data for subsequent runs..
If you want to adjust the axis to more restrictive portion (reduce), then xlim() and ylim() get the job done. Horizontal lines drawn by yline() will persist, as will vertical lines drawn by xline(). Note that xline() and yline() should work for releases including R2018b and later.
% MATLAB R2019a
% Sample Data
n = 10;
X1 = 5*rand(n,1);
Y1 = 5*rand(n,1);
X2 = 5 + 5*rand(n,1);
Y2 = 5 + 5*rand(n,1);
figure, hold on
yline(5)
scatter(X1,Y1,'bo')
scatter(X2,Y2,'rd')
scatter(X1,Y2,'ks')
xlim([0 5])
Notice that by calling xlim() for a larger x-axis range also expands the horizontal line.
xlim([-1,12])
If you plot new data after xlim() outside the range, the plot won't automatically adjust. However, if you do so before calling xlim(), then the horizontal line will expand. Try the example below.
figure, hold on
yline(5)
scatter(X1,Y1,'bo')
scatter(X2,Y2,'rd')
scatter(X1,Y2,'ks')
Then immediately execute
scatter(100*rand(n,1),Y1)
and see that the horizontal line has expanded to cover the new, much longer x-axis.
After posting this answer, I found: How to draw horizontal and vertical lines in MATLAB?
Quite a simple question but just couldn't find the answer online... I want to visualise a point cloud gathered from a lidar. I can plot the individual frames but wanted to loop them to create a "animation". I know how to do it for normal plots with drawnow but can't get it working with a scatter3. If I simply call scatter3 again like I have done in the commented code then the frame that I am viewing in the scatter plot jumps around with every update (Very uncomfortable). How do i get the scatter3 plot to update to the new points without changing the UI of the scatter ie. Still be able to pan and zoom around the visualised point cloud while it loops through.
EDIT: The file is a rosbag file, I cannot attach it because it is 170MB. The problem doesn't happen when using scatter3 in a loop with a normal array seems to be something with using scatter3 to call a PointCloud2 type file using frame = readMessages(rawBag, i).
EDIT: The problem does not seem to be with the axis limits but rather with the view of the axis within the figure window. When the scatter is initialised it is viewed with the positive x to the right side, positive y out of the screen and positive z upwards, as shown in view 1. Then after a short while it jumps to the second view, where the axis have changed, positive x is now out of the screen, positive y to the right and positive z upwards (both views shown in figures). This makes it not possible to view in a loop as it is constantly switching. So basically how to update the plot without calling scatter3(pointCloudData)?
rawBag = rosbag('jackwalking.bag');
frame = readMessages(rawBag, 1);
scatter3(frame{1});
hold on
for i = 1:length(readMessages(rawBag))
disp(i)
frame = readMessages(rawBag, i);
% UPDATE the 3D Scatter %
% drawnow does not work?
% Currently using:
scatter3(frame{1})
pause(.01)
end
The trick is to not use functions such as scatter or plot in an animation, but instead modify the data in the plot that is already there. These functions always reset axes properties, which is why you see the view reset. When modifying the existing plot, the axes are not affected.
The function scatter3 (as do all plotting functions) returns a handle to the graphics object that renders the plot. In the case of scatter3, this handle has three properties of interest here: XData, YData, and ZData. You can update these properties to change the location of the points:
N = 100;
data = randn(N,3) * 40;
h = scatter3(data(:,1),data(:,2),data(:,3));
for ii = 1:500
data = data + randn(N,3);
set(h,'XData',data(:,1),'YData',data(:,2),'ZData',data(:,3));
drawnow
pause(1/5)
end
The new data can be totally different too, it doesn't even need to contain the same number of points.
But when modifying these three properties, you will see the XLim, YLim and ZLim properties of the axes change. That is, the axes will rescale to accommodate all the data. If you need to prevent this, set the axes' XLimMode, YLimMode and ZLimMode to 'manual':
set(gca,'XLimMode','manual','YLimMode','manual','ZLimMode','manual')
When manually setting the limits, the limit mode is always set to manual.
As far as I understood what you describe as "plots jumpying around", the reason for this are the automatically adjusted x,y,z limits of the scatter3 plot. You can change the XLimMode, YLimMode, ZLimMode behaviour to manual to force the axis to stay fixed. You have to provide initial axes limits, though.
% Mock data, since you haven't provided a data sample
x = randn(200,50);
y = randn(200,50);
z = randn(200,50);
% Plot first frame before loop
HS = scatter3(x(:,1), y(:,1), z(:,1));
hold on
% Provide initial axes limits (adjust to your data)
xlim([-5,5])
ylim([-5,5])
zlim([-5,5])
% Set 'LimModes' to 'manual' to prevent auto resaling of the plot
set(gca, 'XLimMode', 'manual', 'YLimMode', 'manual', 'ZLimMode', 'manual')
for i=2:len(x,2)
scatter3(x(:,i), y(:,i), z(:,i))
pause(1)
end
This yields an "animation" of plots, where you can pan and zoom into the data while continuous points are added in the loop
Problem
I am trying to make a 2D figure in Matlab which consists of multiple images and a graph with plot data (which I could eventually convert into an image too). For these images and graph, I need to be able to specify where they are located in my cartesion coordinate system.
For my specific case, it is sufficient to be able to "tell" Matlab where the left-bottom corner of the image is.
So for the example above. I would need some "trick" to let "bird1.jpg" start at position (a,b), "bird2.jpg" at position (c,d) and my plot at position (e,f) in one Matlab figure.
Solution to problem
Thanks to chappjc I was able to find a solution for my problem. Here is the code I used such that other people can use it in the future too.
figure_color = [.741 .717 .42];
axe_color = [1 1 1];
Screen.fig = figure('units','pixels',...
'name','Parallel projection',...
'menubar','none',...
'numbertitle','off',...
'position',[100 100 650 720],...
'color',figure_color,...
'busyaction','cancel',...
'renderer','opengl');
Screen.axes = axes('units','pix',...
'position',[420 460 200 200],... % (420,460) is the position of the first image
'ycolor',axe_color,...
'xcolor',axe_color,...
'color',axe_color,...
'xtick',[],'ytick',[],...
'xlim',[-.1 7.1],...
'ylim',[-.1 7.1],...
'visible','On');
Screen.img = imshow(phantom);
Screen.axes2 = axes('units','pix',...
'position',[0 0 200 200],... % (0,0) is the position of the second image
'ycolor',axe_color,...
'xcolor',axe_color,...
'color',axe_color,...
'xtick',[],'ytick',[],...
'xlim',[-.1 7.1],...
'ylim',[-.1 7.1],...
'visible','On');
Screen.img2 = imshow(phantom);
Basically what I do is first creating a (big) figure, and then create a first axe at a certain position in this big picture, and make it the default axe. In this axe I display my first image (made with the phantom function). After that I make a new axe at a another position and make it again the default axe. After I have done that, I place an image there too (the same picture, but you can also use another one if you want). You can also use handles which is the more clean method, as chappjc describes.
Positioning axes in a figure
One approach would be to manipulate the Position property of multiple axes in a figure. To make multiple axes in a figure:
hf = figure;
ha0 = axes('parent',hf,'Position',[x0 y0 w0 h0]);
ha1 = axes('parent',hf,'Position',[x1 y1 w1 h1]);
Then display your images and plots into the axes by specifying the handle (i.e. ha0 or ha1). For example: image(img0,'Parent',ha0) or imshow(img1,'parent',ha1).
Single Large Image
Another approach is to make a single large image and simply display it with image/imshow/etc.
First for the plots, you can use getframe followed by frame2im to get an image in a matrix format.
Next, decide what goes into your combined image and compute the largest box required to circumscribe the images (using their origins and sizes find the largest x and y coordinate), which includes the origin presumably. Use this info to make a blank image (e.g. img = zeros(h,w,3) for and RGB image).
I have displayed an image and plotted a rectangle over all the useless areas. Now i need to save this image in the form of a matrix, so that i can use it further.
figure,imshow(colz);
hold on;
for i=1:num
if(i~=n)
img=rectangle('Position',box(i,:),'FaceColor','k');
end
end
This is a part of my whole code. I'm covering all the undesired parts with zeros. so now I'm left with my desired area and a background. How can i save the pixel values in another matrix so as to create a new image that contains this enhanced data?
Thanks
here try this
F = getframe(gcf);
% gcf is your figure currently displaying your image with the rectangle
%
y = F.cdata;
hold off
figure(2),imshow(y);