How to plot specific points in matlab?

Question

I've X axis with values [2,6,10] and for Y axis [0.5,0.4,0.2,0.2,....0.5], all values between 0 and 1.

There are certain points which correspond to 2, let's say 1/3rd and the remaining 1/3rd for 6 and remaining 1/3rd for 10. The points corresponding to 2 can have any values between 0 and 1, same applies for point 6 and point 10. How can I plot this?

Answer 1

I guess you have some way to match up each Y-value to its corresponding X-value. By generating a vector of the same length as Y with these X-values they can then be plotted against each other.

The two vectors will then have the following form:

X = [2,6,2,10,6,6,10,2,....6]
Y = [0.5,0.4,0.2,0.2,0.9,0.3....0.5]

Here is a sample code

% X-data
X = [2,6,10];

% Generate random Y-data
n1 = 10;
n2 = 20;
n3 = 30;
n = n1 + n2 + n3;
Y = rand(1,n);

% Match X indices corresponding to Y
% Xall = [2,2,2,...,2,6,6,6,...,6,10,10,10,...,10]
X1 = zeros(1,n1);
X1(:) = X(1);
X2 = zeros(1,n2);
X2(:) = X(2);
X3 = zeros(1,n3);
X3(:) = X(3);
Xall = [X1 X2 X3];

plot(Xall,Y,'o')
xlim([min(X)-2,max(X)+2])

which will generate a figure of the following form

Answer 2

plot(a(1:3:end))

这将绘制每三个点。

Answer 3

a=[0.5,0.4,0.2,0.2,....0.5]
b=[1:3:length(a)]

plot(a(b))