Now I get a matrix named Test with 1000 rows and 2 columns, which contains the (x, y) coordinates of 1000 dots. The first column is the values of X-coordinate, and the second is the values of Y-coordinate.
Now I want to display(plot) all the dots, but I found it's wrong if I just used plot(Test).
Could you guys give me a solution?
It sounds like you want a scatter plot, which you can get by,
plot(Test(:,1), Test(:,2), '*')
You can change the marker to a number of different symbols. For example, 'o' gives a circle, '*' gives an asterisk, '.' gives a point, etc. See the documents for plot for the full list.
If you leave off the marker specification, it will default to no marker with a solid line connecting the points -- not good for a scatter plot!
When you use the single-argument form of plot (i.e. plot(Y)), when Y is a matrix each column of Y is plotted against the row number.
If column 1 represents x and column 2 is y you need to use the two-argument form:
plot(Test(:,1), Test(:,2))
Related
The documentation for it is scarce (in contourc function):
VN is either a scalar denoting the number of lines to compute or a vector containing the values of the lines. If only one value is wanted, set 'VN = [val, val]'; If VN is omitted it defaults to 10.
I've tried a few examples, it somehow affects the amount of lines around my contour.
Does it denote how smooth my function's slope will be?
What does VN stand for?
Explanation
The contourc function does not change your data. It just plots them. Using the VN argument you can control how many contour lines are created between the highest and lowest point of the topography/function you are plotting.
If you set VN to a scalar integer value, it directly specifies the number of lines. VN=20 will create 20 levels between the highest and lowest point of your topography.
If you specify a vector of values you can exactly control at which values in your data the contour line is produced. You should take care that the values are in between min(data(:)) and max(data(:)). Otherwise the lines will not be drawn. Example VN=linspace(min(data(:)),max(data(:)),10) will create the exact same contour lines as not specifying VN.
Examples
To illustrate the effect of VN parameter I give some examples here. I use the contour function to directly plot the lines instead of just calculating them with contourcbut the effect is the same.
% Create coordinate grid
[x,y]=meshgrid(-2:0.1:2,-2:0.1:2);
% define a contour function
z=x.^2 + 2*y.^3;
% create a figure
figure();
% plot contour
contour(x,y,z);
% make axis iso scaled
axis equal
Example 1
Using the contour command without VN argument produces the following result
contour(x,y,z);
Example 2: VN=50
Setting VN to 50
contour(x,y,z,50);
Example 3: VN= vector
Setting VN explicitly to the contour values vector is used here to limit contour lines to a rather narrow range of z data:
contour(x,y,z,linspace(-0.5,0.5,10));
Part of an assignment of mine is to provide a 2D visualisation (plots) of some of my data points that are stored in a matrix. I'm slightly confused because the data is actually in 6D space (i.e. each row has 6 columns like 0 1 0 8 8 2).
Is there something I'm missing or does this genuinely not make sense? Is this something MATLAB can do?
Edit: Is something like this possible?
Though I wouldn't consider it visualizing 6D data, you can get the linked plot with a simple call to plot:
A = rand(6);
x = 1:6;
plot(x,A'); % Transpose A to plot rows since it's square, see plot documentation
Which produces the following:
From the documentation:
If one of X or Y is a vector and the other is a matrix, then the
matrix must have dimensions such that one of its dimensions equals the
vector length. If the number of matrix rows equals the vector length,
then the plot function plots each matrix column versus the vector. If
the number of matrix columns equals the vector length, then the
function plots each matrix row versus the vector. If the matrix is
square, then the function plots each column versus the vector.
Simply use:
surf(2Dmatrix)
You can read more here: http://uk.mathworks.com/help/matlab/ref/surf.html
If your matrix is 2D image, simply use
figure; imshow(2Dmatrix, [])
If you leave the square bracket empty, the limit will be automatic. When the figure is displayed you can change it to different colormap by Edit > Colormap.
I am trying to plot 3 vectors onto matlab GUI in a serial object's callback.
I want to plot this on axes handle but the problem is it only plot last vector;
plot(handles.axes1,sensor1,'r');
plot(handles.axes1,sensor2,'b');
plot(handles.axes1,sensor3,'g');
I searched on internet and find that this issue can be solved with hold on and hold of feature so I tried this
plot(handles.axes1,sensor1,'r');
hold on ;
plot(handles.axes1,sensor2,'b');
plot(handles.axes1,sensor3,'g');
hold off;
but in this case a new figure is opened(dont know why) and again only the last plot is drawn.
I am stucked. If any one have idea of what would be the issue?
Thanks
I'm not sure why your first try using "hold" didn't work. Seems like it should have.
But in any case, you can get the desired behavior in a single command:
plot(handles.axes1,length(sensor1),sensor1,'r',...
length(sensor2),sensor2,'b',...
length(sensor3),sensor3,'g');
This specifies both an X = length(sensor_) and a Y = sensor_ to the plot command. When you only give plot a Y input, it assumes an X of length(Y). But you can't combine multiple traces in a single plot command by giving only the Y input for each, because it will try to treat the inputs as X,Y pairs.
As the vectors are the same length we can simply combine them as the columns of a matrix and then plot the matrix
plot(handles.axes1,[sensor1',sensor2',sensor3'])
However these will have the default colour order. Without specifying x values setting colors within the plot command is tricky. However (luckily) the default order starts:
blue,green,red...
so swapping the column order will plot the lines with the colours requested
plot(handles.axes1,[sensor2',sensor3',sensor1'])
(this assumes the vectors are rows, if they are columns don't transpose them)
I would like to create a plot with several lines, each corresponding to a row at a given matrix.
To be more elaborate, I have got a matrix M where each row represents a value that is changing along the columns. I would like to plot this change as a function of the column index to each of the rows, so to plot (e.g) the first rowI should :
plot(M(1,:));
The thing is, I would like to plot all the rows. Of course I could iterate over them, hold and plot the current one:
(plot(M(i,:))
but I'm wondering if there's a simple command or a single-liner that would do it.
I have tried plotmatrix but without much success regarding the desirable results.
Thanks!
Have you tried plot(M')?
From the first paragraph of the documentation of plot:
plot(Y) plots the columns of Y versus the index of each value when Y is a real number.
I have multiple vectors of varying lengths that I would like to plot next to each other in 3D space in Matlab.
As an example:
Say I have three vectors:
X is a 5x2 vector,
Y is a 10x2 vector and
Z is a 15x2 vector.
Each element of every vector has the format:
x value, y value
but the x values of the various vectors do not match.
I would like to plot these vectors in 3D space, next to each other. The reason why I don't want to plot them using "hold" is because most of the data have the same values, but I would like to see how many of the plots have the same value at a specific time.
I hope my questions makes sense. Please just ask if anyone is unsure.
I think you are looking for the function ribbon.
Documentation: http://www.mathworks.fr/help/techdoc/ref/ribbon.html
EDIT:
if your x's do not have the same length, you can combine it with interp1 as follow:
x1=0:0.1:1;
x2=0:0.02:1.5;
y1=x1.^2;
y2=sqrt(x2);
y2=interp1(x2,y2,x1);
ribbon(x1',[y1;y2]')