Plot vertical lines at a certain time - matlab

Question

I want to plot a line at a certain "x" (being a scalar) value so every second, a vertical line with certain values will be drawn. I know that one way to plot a vertical line (without considering time) is to declare a vector like:
y=0:0.01:5;
or something like:
y=3:0.01:6;
and write plot(x,y);
Also, I've done "animated" plots using the "pause" parameter but I don't know how to do that in this case. Thanks for your help.

Answer 1

Another way I can suggest is to use plot in combination with hold on. With plot, you'd only specify two points where each point has the same x value, but the y value can change to whatever you want. When you draw points using plot, the default behaviour is that a line is drawn in between the points. If we specify two points having the same x coordinate, but different y coordinates, we would essentially draw a vertical line in between these points.
For example, given that you want to have every "second" have a vertical line, we can do something like this:
ystart = [-1 -2 -3 -1 -2 -3];
yend = [1 2 3 1 2 3];
figure; hold on;
for idx = 1 : numel(ystart)
plot([idx idx], [ystart(idx) yend(idx)]);
end
This is what we get:
We define two arrays of 6 elements where ystart denote the starting y point and yend denote the ending y point. We spawn a new figure, use hold on to plot multiple lines on the same graph, then use a for loop with plot so that we draw a line in between two points: (x,y) = (idx, ystart(idx)) and (x,y) = (idx, yend(idx)). idx goes from 1 to 6. Obviously, you can change the location of where the x values are being plotted by specifying another array... call it x:
x = 0:2:10; %// Time values
ystart = [-1 -2 -3 -1 -2 -3];
yend = [1 2 3 1 2 3];
figure; hold on;
for idx = 1 : numel(ystart)
plot([x(idx) x(idx)], [ystart(idx) yend(idx)]);
end
Here, we will draw vertical lines starting from x = 0 up to x = 10 in steps of 2. The result would basically be the same, but the x values would be different, as well as where the vertical lines are being drawn.

Answer 2

There are several ways to plot vertical lines in Matlab. The easiest recommendation is the line function:
line(X,Y) adds the line defined in vectors X and Y to the current
axes. If X and Y are matrices of the same size, line draws one line
per column.
Call this as many times as you want.
h=line(X,Y)
will give you properties of the line
Another way is to
X= X0*(Y./Y)
then
plot(X,Y)
will plot a vertical line at the point X0. Another thing you can do is draw a line using the above line function from the point (X0, min(Y)) to the point (X0, max(Y)) which is the most elegant solution. If you are trying to create a movie, you will need to access the properties of this line using h=line(X,Y). To move the line to a new position, you will have to set the properties of this line by calling set(h, Property, value). For example in your movie, you need to move it to a new position so you will set that property. This way, by minimum change of data, you can move a line or show its accelerating.