Plotting specific values of 2xn array based on values in first row

Hello! I have 2xn arrays. The first row contains values between 1 and 6 that code specific events that happened at the timepoints that are saved in the second row. Something like this:

   1   4   5   1   5
  200 350 360 400 600

Goes on like that. It's probably really basic. I want to plot only the timepoints in the second row for the specified event codes in the first row. I hope this is clear. Thanks!

Answer 1

[Sebastian Castro]

You want to be looking at row 1 for every index that matches a certain value... let's take 5 for this example.

row1 = x(1,:);
indices = (row1 == 5);

Then, you want to use those indices to index into row 2:

row2 = x(2,:);
output = row2(indices);

Now, this has a lot of intermediate variables, so you might instead want to do it all in one shot:

output = x(2,x(1,:)==5);

- Sebastian

Answer 2

[Rose]

I think you mean like this:

>> x=[1 4 5 1 5;200 350 360 400 600];

>> plot(x(1,:),x(2,:))

You even can add more details to the plot or set the axis limits:

>> plot(x(2,:),x(1,:),'*','LineWidth',1);

>> axis([100 700 0 6]);

xlabel('Time')

ylabel('Values')