Controlling the spacing between markers in a plot in a figure

How do I control the spaces between markers in a plot so that it although I am plotting say a 100,000 points but it shows markers at only sample points, and does not show markers when the plot drops between two points:

A sample is shown in figure below:

http://postimage.org/image/7zdghqtzn/

Thanks

Answer 1

[Image Analyst]

I'm not sure why my answer to your duplicate question at http://www.mathworks.com/matlabcentral/answers/57241#answer_69235 didn't work for you. Walter and I are both saying the same thing: plot a subset of your data:

plot(allYourData, 'r-');
hold on;
plot(allYourData(1:10:end), 'bo'); % Or can use scatter.

or something like that. You can pick them at random, or pick every 10th one like I did above or some other subsampling period.

[Walter Roberson]

plot(1:10:numel(allYourData), allYourData(1:10:end), 'bo')

to get the x axis correct relative to plot(allYourData)

[Sam Alex]

you are right, but when I convert the y-scale to log, all these markers get mixed up and change position...the final plot should use the log or it wont be clear, so how do I go around this so that the markers are clear as the original linear plot?

Thanks

[Image Analyst]

They don't get mixed up. How could that happen? It doesn't. You can go ahead and plot on a loglog, semilogx or semilogy and they won't change order. Everything is exactly where it should be. If you say they are not, then post code and a screenshot to prove it.

[Sam Alex]

You are right...I just got my brain mixed up...lots of figures :(

Thanks man...your expertise is wonderful :)

Thanks for helping me...I appreciate it..

Answer 2

[Walter Roberson]

plot() once without any markers on the line. Then scatter() the desired markers into place.

[Sam Alex]

Do you think in that plot I gave as an example, he selected them at random? They dont look random

[Walter Roberson]

? I did not say anything about random ?

The plots you gave as examples look to me to be straight lines between the markers, as if only those points had been plotted, a marker for each point.

[Sam Alex]

it goes from 0-100,000?

[Walter Roberson]

Yes, remember that plot(x,y) places the points at the given x locations. For example,

x = 0:1000:100000;
y = x.^2;
plot(x,y);

That will have an x axis from 0 to 100000 even though only 100 points are plotted.

Answer 3

[Jacob Jonsson]

I wrote a function available at: https://www.mathworks.com/matlabcentral/fileexchange/37165-plotsparsemarkers Should work with MATLAB versions that have 'MarkerIndices' as well as the older ones.