I have the following matlab code for approximating a differential equation via the Euler-method:
% Eulermethod
a=0;
b=0.6;
Steps=6;
dt=(b-a)/Steps;
x=zeros(Steps+1,1);
x(1,1)=1;
y=zeros(Steps+1,1);
for i=1:Steps
x(i+1,1)=x(i,1)+dt*(x(i,1)*x(i,1)+1);
end
plot(x)
I want to be able to plot the solution plot for several different values of Steps in one plot and have the x-axis go from 0 to 0.6 instead of from for example 1 to 100 000 etc. Can this be done?
If you use the hold on command this will allow you achieve multiple plots on the same figure. Similarly, if you separate your data into x and y vectors, you can plot them against eachother by passing 2 vectors to plot instead of just one. For example
figure
hold on
for i=1:m
x = [];
y = [];
%% code to populate your vectors
plot(x,y)
end
You should now see all your plots simultanesously on the same figure. If you want x to be composed of n equally spaced elements between 0 and 0.6, you could use the linspace command:
x = linspace(0.0,0.6,n);
In order to distinguish your plots, you can pass an extra paramter to the function .For example
plot(x,y,'r+')
will plot the data as a series of red + symbols.
Plot can take more arguments: plot(x_axis,values, modifiers);
If x-axis is a vector of M elements, values can be a matrix of MxN elements, each of which are drawn with a separate color.
Related
The thing is i have a matrix and when i use imagesc() it goes like this but my goal is this.
So my question is does any one know which plot is this or some one has document about this, thanks.
If you have two vectors r and theta that give the polar coordinates, or two matrices rGrid and thetaGrid that give the polar coordinates for each element of the data matrix, then code like this will work:
r=linspace(1,20,20);
theta=linspace(0,2*pi,20);
data = r'.*sin(2.*theta); % INSERT DATA HERE
[thetaGrid,rGrid]=meshgrid(theta,r); % Create coordinate grid if needed
[xGrid,yGrid]=pol2cart(thetaGrid,rGrid);
surf(xGrid,yGrid,data); % Plot data
view(2);
Just keep in mind that the rows of the data matrix need to correspond to different radii, and columns need to correspond to different values of theta. If it's flipped, then transpose the matrix before plotting:
data = data';
Also, if the data doesn't wrap around from 0 to 2*pi radians, then repeat the first value of theta as the last value, and repeat the first column of the data matrix as a new final column:
theta(end+1)=theta(1);
data=cat(2,data,data(:,1));
There is also a 3D Polar Plot function on the MATLAB file exchange, but I do not have any experience using it: 3D Polar Plot
Consider the following data points and plots
a = randi(50,1,200);
b = randi(50,1,200);
figure;scatter(a,b,'.')
figure;plot(a,b,'.')
When we run the following code , we receive exactly the same plots for a against b , my question is why should we even use or to rephrase again in what conditions scatter plot has advantage over plot function ? because plot seem to have more formatting options that the scatter function
plot has a concept of the order of the points mattering so you can use it to make line plots. plot also allows you to specify the input x and y values as either vectors or matrices or allows you to input multiple x and y vectors both of which allow you to plot multiple series at once:
whereas scatter only allows you to input 1 x and 1 y and they both have to be vectors. However, 'scatter' allows you to specify an area and colour vector to affect the points individually i.e.
I am trying to plot the following simple function; $y=A.*x$ with different A parameter values i.e. A=0,1,2,3 all on the same figure. I know how to plot simple functions i.e. $y=x$ by setting up x as a linspace vector so defining x=linspace(0,10,100); and I know that one can use the hold command.
I thought that one could simply use a for loop, but the problem then is getting a plot of all the permutations on one figure, i.e. I want a plot of y=t,2*t,3*t,4*t on the same figure. My attempt is as follows:
x=linspace(0,10,100);
%Simple example
Y=x;
figure;
plot(Y);
%Extension
B=3;
F=B*x;
figure;
plot(F);
%Attempt a for loop
for A= [0,1,2,3]
G=A*x;
end
figure;
plot(G);
This is how I would plot your for loop example:
figure;
hold all;
for A=[0,1,2,3]
G=A*x;
plot(G);
end
figure creates a new figure. hold all means that subsequent plots will appear on the same figure (hold all will use different colours for each plot as opposed to hold on). Then we plot each iteration of G within the loop.
You can also do it without the loop. As with most things in Matlab, removing the loop should give improved performance.
figure;
A=[0,1,2,3];
G=x'*A;
plot(G);
G is the outer product of the two vectors x and A (with x having been transposed into a column vector). plot is used to plot the columns of the 100x4 matrix G.
Am trying to plot 2 variable of different size length in matlab GUI using push button,
but because the variables are of different length it will not work,is there a way i can make it to plot.
d= pdist([x,y,z],'euclidean') ; % value of my distance
dd= 1:10:d; % interval and end 'd' value
FSL=-120; %value of free space loss get from the GUI
DFSL= 1:10:FSL %interval and end at FSL value
plot(dd,DFSL)
The plot code didnt work coming back with an error "
Error using plot
Vectors must be the same lengths"
You can plot vectors of two different lengths, but not against each other. You have used the syntax
plot(x,y)
which means for every element in vector x, there should be a corresponding element in vector y. In your case, you do not have this, hence the error.
You can plot like this though:
plot(x)
figure;
plot(y)
If you are looking to plot them in a single plot, subplot will be useful.
Hi
I was wondering if there is any way to get all points which was drawn on Matlab plot. Let's say that I drawn one line on plot and to draw this line I used just two points - matlab ploter connected these points and I get a line. Is there any way to get all the points which are on that line, without saving this plot to file ??
If you plot a line from two points, e.g. plot([x1 x2],[y1 y2]), the easiest way to get all the plots on the line is to calculate them directly.
nPts = 100; %# number of points on the line you want
%# listOfPoints is a 2-by-nPts array with all the points on the line
listOfPoints = [x1:(x2-x1)/(nPts-1):x2;y1:(y2-y1)/(nPts-1):y2];
You can generate the points you are looking for through basic linear regression. Feed in your x and y variables to Matlab's regression function and it calculates the coefficients of the line of plot(x,y). With the line equation set up, you can feed in a list of new x variables and it will calculate the corresponding y values.
x=[x1; x2];
y=[y1; y2];
b = regress(y,[ones(length(x),1) x])
new_y=b(1)+b(2)*[new_x1:new_x2]