I am using MATLAB to plot two lines of a time series... (a min and max line)
I have the points converging at a single point at the end of the data.
I am trying to fill the area in between the lines and then plot other lines on top of the shaded area.
Here is my problem:
When I use "fill" it does exactly what I want it to do...but it draws a line from the last point of the data back to the initial data point. How do I get rid of it?
Here is a very vague sketch of my 2 examples:
The line below the graph is what I am talking about...
Any ideas how to avoid that?
Thanks!
I guess that you create the fill with
fill([xData1;xData2],[yData1;yData2])
where xData1 is a n-by-1 array of x-data for your first curve. This will lead to a weirdly-shaped polygon because the 'corners' of the polygon are not properly ordered.
Instead, you should do
fill([xData1;xData2(end:-1:1)],[yData1;yData2(end:-1:1])
i.e. flip the order of one of the two data sets.
As #Jonas explained (beat me to it), you need to properly order the data of the two time-series. Let me add an example to that:
%# first series
x1 = linspace(pi/4, 5*pi/4, 100);
y1 = cos(x1);
%# second series
x2 = linspace(pi/4, 5*pi/4, 100);
y2 = sin(x2);
subplot(121), fill([x1 x2], [y1 y2], 'r')
subplot(122), fill([x1 fliplr(x2)], [y1 fliplr(y2)], 'r')
hold on
plot(x1,y1, 'Color','b', 'LineWidth',3)
plot(x2,y2, 'Color','g', 'LineWidth',3)
Related
I was wondering if you could advise me how I can connect several points together exactly one after each other.
Assume:
data =
x y
------------------
591.2990 532.5188
597.8405 558.6672
600.0210 542.3244
606.5624 566.2938
612.0136 546.6825
616.3746 570.6519
617.4648 580.4575
619.6453 600.0688
629.4575 557.5777
630.5477 584.8156
630.5477 618.5906
639.2696 604.4269
643.6306 638.2019
646.9013 620.7697
652.3525 601.1584
"data" is coordinate of points.
Now, I would like to connect(plot) first point(1st array) to second point, second point to third point and so on.
Please mind that plot(data(:,1),data(:,2)) will give me the same result. However, I am looking for a loop which connect (plot) each pair of point per each loop.
For example:
data1=data;
figure
scatter(X,Y,'.')
hold on
for i=1:size(data,1)
[Liaa,Locbb] = ismember(data(i,:),data1,'rows');
data1(Locbb,:)=[];
[n,d] = knnsearch(data1,data(i,:),'k',1);
x=[data(i,1) data1(n,1)];
y=[data(i,2) data1(n,2)];
plot(x,y);
end
hold off
Although, the proposed loop looks fine, I want a kind of plot which each point connect to maximum 2 other points (as I said like plot(x,y))
Any help would be greatly appreciated!
Thanks for all of your helps, finally a solution is found:
n=1;
pt1=[data(n,1), data(n,2)];
figure
scatter(data(:,1),data(:,2))
hold on
for i=1:size(data,1)
if isempty(pt1)~=1
[Liaa,Locbb] = ismember(pt1(:)',data,'rows');
if Locbb~=0
data(Locbb,:)=[];
[n,d] = knnsearch(data,pt1(:)','k',1);
x=[pt1(1,1) data(n,1)];
y=[pt1(1,2) data(n,2)];
pt1=[data(n,1), data(n,2)];
plot(x,y);
end
end
end
hold off
BTW it is possible to delete the last longest line as it is not related to the question, if someone need it please let me know.
You don't need to use a loop at all. You can use interp1. Specify your x and y data points as control points. After, you can specify a finer set of points from the first x value to the last x value. You can specify a linear spline as this is what you want to accomplish if the behaviour you want is the same as plot. Assuming that data is a 2D matrix as you have shown above, without further ado:
%// Get the minimum and maximum x-values
xMin = min(data(:,1));
xMax = max(data(:,1));
N = 3000; % // Specify total number of points
%// Create an array of N points that linearly span from xMin to xMax
%// Make N larger for finer resolution
xPoints = linspace(xMin, xMax, N);
%//Use the data matrix as control points, then xPoints are the values
%//along the x-axis that will help us draw our lines. yPoints will be
%//the output on the y-axis
yPoints = interp1(data(:,1), data(:,2), xPoints, 'linear');
%// Plot the control points as well as the interpolated points
plot(data(:,1), data(:,2), 'rx', 'MarkerSize', 12);
hold on;
plot(xPoints, yPoints, 'b.');
Warning: You have two x values that map to 630.5477 but produce different y values. If you use interp1, this will give you an error, which is why I had to slightly perturb one of the values by a small amount to get this to work. This should hopefully not be the case when you start using your own data. This is the plot I get:
You'll see that there is a huge gap between those two points I talked about. This is the only limitation to interp1 as it assumes that the x values are strictly monotonically increasing. As such, you can't have the same two points in your set of x values.
i'm simulating a wave propogation in time and place. i want to make a colormap of its values for every time step, in space. i mean, i want to make a figure of 2 axes (x and y) and displays the wave's values at those points by color (the wave varible is V).
how can i do it?
i'v tried:
for ind1 = 1:length(t)
figure()
trisurf(x1,y1,V(:,ind1),'EdgeColor', 'None', 'facecolor', 'interp');
view(2);
end
but i got a message that z (=V) suppose to be a function and not a scalar.
any suggestions?
I have two options, I don't think they will be perfect, but it might help.
First, interpolate the data onto a rectangular mesh and use contourf:
F=scatteredInterp(x,y,V(:,ind1));
X=linspace(min(x),max(x));
Y=linspace(min(y),max(y));
contourf(X,Y,F(X,Y))
Secondly, use scatter to plot points with varying colour:
scatter(x,y,25,V(:,ind1))
where the 25 controls the size of each marker, you may have to experiment with it.
Hope that gives you some ideas.
i've made a loop that finally works:
clear heart_movie
Vnorm = mat2gray(V(:,1:2000));
x1_new = x1-min(x1)+1;
y1_new = y1-min(y1)+1;
for ind1 = 1:2000
heart = zeros(max(x1_new),max(y1_new));
z = Vnorm(:,ind1);
for ind2 = 1:length(z);
heart(y1_new(ind2),x1_new(ind2))= z(ind2);
end
colormap(jet);
imagesc(flipud(heart));
end
Im trying to create a triangle wave in matlab with equal rise and fall slope.
I searched around abit and found a code example:
n=input ('Enter the length of the sequence N= ');
t=0:n;
y=(-1).^t;
stem(t,y);
ylabel ('Amplitude');
xlabel ('Time Index');
TITLE ('Triangular waveform');
This code creates the the triangle form, but there are only data plots at the tip of each triangle. I want more data plots that follow the lines of the triangles.
Is there any function in matlab that can fill in data points with a specific width between the plots in the plotted lines from the graph?
If no, how am I supposed to solve this?
You need to linearly interpolate:
t2 = 0:0.5:n;
y2 = interp1(t, y, t2);
where t and y are the arrays from your example. You can use any size of interval for t2:
t2 = 0:0.1:n;
for example.
Change t=0:n; to t=0:0.1:n; and y=(-1).^t; to y=2*abs(mod(t,2)-1)-1;
This is what I got:
I'm trying to use Matlab for some data plotting. In particular I need to plot a series of lines, some times given two points belonging to it, some times given the orthogonal vector.
I've used the following to obtain the plot of the line:
Line given two points A = [A(1), A(2)] B = [B(1), B(2)]:
plot([A(1),B(1)],[A(2),B(2)])
Line given the vector W = [W(1), W(2)]':
if( W(1) == 0 )
plot( [W(1), rand(1)] ,[W(2), W(2)])
else
plot([W(1), W(1) + (W(2)^2 / W(1))],[W(2),0])
end
where I'm calculating the intersection between the x-axis and the line using the second theorem of Euclid on the triangle rectangle formed by the vector W and the line.
My problem as you can see from the picture above is that the line will only be plotted between the two points and not on all the range of my axis.
I have 2 questions:
How can I have a line going across the whole axis range?
Is there a more easy and direct way (maybe a function?) to plot the line perpendicular to a vector? (An easier and more clean way to solve point 2 above.)
Thanks in advance.
Do you know the bounds of your axis for displaying the plot? If so, you can specify the range of the plot with the axis([xmin, xmax, ymin, ymax]) function.
So, from your question, if you know the slope m and intercept b, you can make sure your function plots the line across the whole window by specifying:
plot([xmin, xmax], [m*xmin + b, m*xmax + b]);
axis([xmin, xmax, min(m*xmin+b, m*xmax+b), max(m*xmin+b, m*xmax+b)]);
where xmin and xmax are values you specify as the range of your x-axis. This will make your line go from the corner of your plot to the other corner. If you want a buffer in the y-direction, then add one like so:
buffer = 5; % for example, you set this to something that looks good.
axis([xmin, xmax, min(m*xmin+b, m*xmax+b)-buffer, max(m*xmin+b, m*xmax+b)+buffer]);
I have a question about using the area function; or perhaps another function is in order...
I created this plot from a large text file:
The green and the blue represent two different files. What I want to do is fill in the area between the red line and each run, respectively. I can create an area plot with a similar idea, but when I plot them on the same figure, they do not overlap correctly. Essentially, 4 plots would be on one figure.
I hope this makes sense.
Building off of #gnovice's answer, you can actually create filled plots with shading only in the area between the two curves. Just use fill in conjunction with fliplr.
Example:
x=0:0.01:2*pi; %#initialize x array
y1=sin(x); %#create first curve
y2=sin(x)+.5; %#create second curve
X=[x,fliplr(x)]; %#create continuous x value array for plotting
Y=[y1,fliplr(y2)]; %#create y values for out and then back
fill(X,Y,'b'); %#plot filled area
By flipping the x array and concatenating it with the original, you're going out, down, back, and then up to close both arrays in a complete, many-many-many-sided polygon.
Personally, I find it both elegant and convenient to wrap the fill function.
To fill between two equally sized row vectors Y1 and Y2 that share the support X (and color C):
fill_between_lines = #(X,Y1,Y2,C) fill( [X fliplr(X)], [Y1 fliplr(Y2)], C );
You can accomplish this using the function FILL to create filled polygons under the sections of your plots. You will want to plot the lines and polygons in the order you want them to be stacked on the screen, starting with the bottom-most one. Here's an example with some sample data:
x = 1:100; %# X range
y1 = rand(1,100)+1.5; %# One set of data ranging from 1.5 to 2.5
y2 = rand(1,100)+0.5; %# Another set of data ranging from 0.5 to 1.5
baseLine = 0.2; %# Baseline value for filling under the curves
index = 30:70; %# Indices of points to fill under
plot(x,y1,'b'); %# Plot the first line
hold on; %# Add to the plot
h1 = fill(x(index([1 1:end end])),... %# Plot the first filled polygon
[baseLine y1(index) baseLine],...
'b','EdgeColor','none');
plot(x,y2,'g'); %# Plot the second line
h2 = fill(x(index([1 1:end end])),... %# Plot the second filled polygon
[baseLine y2(index) baseLine],...
'g','EdgeColor','none');
plot(x(index),baseLine.*ones(size(index)),'r'); %# Plot the red line
And here's the resulting figure:
You can also change the stacking order of the objects in the figure after you've plotted them by modifying the order of handles in the 'Children' property of the axes object. For example, this code reverses the stacking order, hiding the green polygon behind the blue polygon:
kids = get(gca,'Children'); %# Get the child object handles
set(gca,'Children',flipud(kids)); %# Set them to the reverse order
Finally, if you don't know exactly what order you want to stack your polygons ahead of time (i.e. either one could be the smaller polygon, which you probably want on top), then you could adjust the 'FaceAlpha' property so that one or both polygons will appear partially transparent and show the other beneath it. For example, the following will make the green polygon partially transparent:
set(h2,'FaceAlpha',0.5);
You want to look at the patch() function, and sneak in points for the start and end of the horizontal line:
x = 0:.1:2*pi;
y = sin(x)+rand(size(x))/2;
x2 = [0 x 2*pi];
y2 = [.1 y .1];
patch(x2, y2, [.8 .8 .1]);
If you only want the filled in area for a part of the data, you'll need to truncate the x and y vectors to only include the points you need.