Stair Plot problem

I have four data points along a date axis, which I want to plot as a stairs.

the data are

Data = [9;9;10;9]

the dates are in chronological order, but don't really mater here I think.

My problem is that when plotting as

stairs(Dates,Data)

matlab marks six data points instead of the actual four. I realize that this is necessary in order to do the corners, but isn't there a way to keep the line while having the markers only on the actual datapoints.

And more importantly, as it is now the plot rises to 10 (and has a marker at 9 at the same time) before the matching date, and goes back to 9 at the time it should be 10.

Is there any property I need to change in order to get the output I want?

Answer 1

[Fangjun Jiang]

I guess that is what the way stairs() is designed.

To answer your first part of the question, you probably need to do two steps.

Data=[9;9;10;9];
figure;
stairs(Data);
hold on;
plot(Data,'*');
axis([0 5 8 11]);

I am not very clear about your second part of the question. Maybe this?

Data=[9;9;10;9];
figure;
stairs([Data;Data(end)]);
hold on;
plot(Data,'*');
axis([0 5 8 11]);

[Patrick Saegesser]

Thanks for your answer. Sorry that I wasn't too clear.

I'll have to try, but I think the first part part should work in two steps as you described. I don't understand why it marks points that are not in the dataset, but as you said, it may the way it is designed.

Regarding the second question, using your axis points, I want the plot to reflect that the Date is always the first point in time on a given level, and the y value remains there until a new event occurs.

Currently, the step from y=9 to y=10 takes place at x=5, remains there on x=8 and drops to y=9 there. Thus I have two points where y=10 and y=9 at the same x value, one at x=5, the other at x=8.

I would like to have it rise to y=10 at x=8 and remain there until x=11, where it then drops back.

[Fangjun Jiang]

I think you may have some inconsistency describing your data in your comments. I can think of a way to show the drop of y from 10 to 9 at x=8, but I don't see why x=11 comes to the picture.

%%

Data=[9;9;10;9];

x=[1;3;5;8];

figure;

stairs([x;x(end)+1],[Data;Data(end)]);

hold on;

plot(x, Data,'*');

axis([0 10 8 11]);