# Plotting multiple Y scales49

Posted by Doug Hull,

Often times, people want to plot two vectors of data with the same x-axis, but the vectors are at wildly different values on the y-axis. The vector with the smaller y values will often be just a flat line if you use the same scale for both. For that reason, things like plotyy were invented.

Zhipeng was not satisfied with our implementation, so he made his own with LayerPlot. Compare the difference!

Josh replied on : 1 of 49

Hi Doug,

I would like my data to be plotted as points, not lines. Can I make a multiple y axes plot using points?

Doug replied on : 2 of 49

The commands you are looking for are PLOTYY (to get multiple Y axis) and you want to specify the marker when doing a plot.

>>plot(x,y,’.’)

will plot x vs y with dots but no lines connecting.

Doug

Erik replied on : 3 of 49

Is there a way to plot with plotyy with several series associated with the first axis, and one with the second? I can get plotyy working with two series, one with each y-axis, but not when I start having more data series…

thanks
Erik

Sulabh Dhanuka replied on : 5 of 49

Doug,

Both plotyy and plotyyy (that you link to above) only allow for one data series on each axis. They do not allow for say multiple series on one axis and another series on another axis. Is there any way to plot that?

Thanks,
Sulabh

Eric replied on : 6 of 49

I guess most of the people here run into the following problem :
[ax,h1,h2]=plotyy(im_x,im_y,x,y1);
hold on
plot(ax(2),x,y2)

This usually returns error:
??? Error using ==> plot
Parent destroyed during line creation

When debugging into plot() you find a newplot.m — in there the right parent figure is selected, because even graphical objects need a father! In the same file there is the function
ObserveAxesNextPlot() which deletes the axes we try to plot into *if* the “nextplot” property is not set to “add”.
Hence:

[ax,h1,h2]=plotyy(x, y1, x, y2);
hold on
%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%
plot(ax(2),x,y3)
hold off

Now sit back and behold that beauty.

jiro replied on : 7 of 49

Another solution is to use the “line” command. LINE is a low-level function that does not call “newplot”.

[ax, h1, h2] = plotyy(x, y1, x, y2); line(x, y3, 'Parent', ax(2)); 

Bob replied on : 8 of 49

I’ll second Jiro’s tip. Some years ago I rewired my brain to start using PLOT, LINE, LINE whenever possible instead of PLOT, HOLD ON, PLOT, PLOT. Initially it was just laziness (less typing). Fewer missed HOLD OFF cases to debug was a plus. Code readability improved without HOLD state. Good tip.

Eric replied on : 9 of 49

Wasn’t aware of the line function for such uses. Certainly better than setting weird axis properties.
Cheers, jiro.

Tobias replied on : 10 of 49

Hallo there,

I have a question to the above mentioned methods:
I already managed to plot up to 3 datasets in one plot window with the PLOTYY function. But there are still unsolved problems:
1.
Is it possible to add a second dataset to the first y-axis? (I only managed to add a second dataset to the second y-axis)

2. (Most important to me!)
Is it possible to (easily) manipulate the zoom-function in PLOTYY-plots so that the y-axes gets updated when I zoom in? At the moment the axis-settings are very crude and they dont update, when I zoom in the window, so that I wont have any axis-ticks, when I zoom in deeply.

I would be very grateful for helpful answers without using aditional software packages, because the written programm shall be used by other people, too.

Best regards
Tobias

Doug replied on : 11 of 49

Tobias,

This code will do what you want. Basically, calling to the individual axes to get things done.

clf
x = 0:0.01:20;
y1 = 200*exp(-0.05*x).*sin(x);
y2 = 0.8*exp(-0.5*x).*sin(10*x);
[AX,H1,H2] = plotyy(x,y1,x,y2,’plot’);
hold(AX(1), ‘on’)
axes(AX(1))
plot (1:20, rand(1,20)*200)
hold(AX(2), ‘on’)
axes(AX(2))
plot (1:20, rand(1,20)-0.5)
hold(AX(2), ‘off’)

Tobias replied on : 12 of 49

Hi Doug,

first off thanks a lot for the quick response!
Second I have a question concerning the code:
I didn’t implement it yet, but from my understanding I can’t see a part, that enables the zooming with adjusting axes-ticks.
Is there a way to do that?

Tobias

Tobias replied on : 13 of 49

Hi again,

I now had the chance to test the algorithm and I had a problem:
The first addition with hold(ax(1), ‘on’) worked out fine, but on the other hand, I managed to realize this function another way before.
But where I am stuck is the second addition with (hold(ax(2),’on’) or more precisely the “closing tag” (hold(ax(2), ‘off). Because, when I try to implement this, I get the error message:
“??? Error using ==> hold at 69
Unknown Command option”

For me, it looks like Matlab won’t supply the function of adding more than 1 dataset to the second axis.

Additionally, there is still the problem mentioned above with the non-changing axis-ticks. Is that meant to be solved be the ‘plot’ keyword in the function call of “plotyy”? At least it didn’t work, if it should :(

Any clues?

Doug replied on : 14 of 49

It looks like you are missing the close quote on ‘off.

I can not modify the zoom behavior of plotyy. It is not clear how zooming should work there. You can change the ylim of each axis though.

-Doug

Andrew replied on : 15 of 49

When you have the 2 y axis’s, how do you change the scale for the on on the right side? I’ve been mainly using the gui to edit any changes to my graphs.

Doug replied on : 16 of 49

Andrew,

x = 0:0.01:20;
y1 = 200*exp(-0.05*x).*sin(x);
y2 = 0.8*exp(-0.5*x).*sin(10*x);
[AX,H1,H2] = plotyy(x,y1,x,y2,’plot’);

%% Take a look at limits then

set(AX(2), ‘ylim’, [-1 1])

Doug

Lyle replied on : 17 of 49

Hi

I have read through these comments and noted that they all require plotyy.

Is there a way to add a second axis after a call to plot?

I’m using a third-party graphing tool and wish to overlay some of my own stuff??
thanks, Lyle

Zach replied on : 19 of 49

Hi,

I’m trying to plot several (7) data sets that all have a common y axis (depth). Each data set has different units and scales. What I’d like to do is plot one y axis on the left side and seven different x axes along the bottom, side by side. Do you have any tips for accomplishing this?

Thanks!

Doug replied on : 20 of 49

This sounds akin to the PLOTYY function, or the MATLAB Central File Exchange file PLOTYYY.

I have not heard of people doing this for X. I am sure it can be done, but 7 is a bit excessive for this format. Have some sample data you can post images of to egt an idea what you are dealing with?

Doug

Zach replied on : 21 of 49

I’m working with geophysical data, so I’d like to produce a depth profile. The y-axis would be depth, from 0 (surface) down to about 100 km let’s say, in increments of 10 km. At each depth I have calculated various properties, such as density, viscosity, temperature, etc, which would be plotted along the x-axis. I’d like to create, on one graph, one line for each of these properties, each with their own scale on the x-axis. Here’s a hypothetical example of some data:

depth = [0 10 20 30 40 50 60 70 80 90 100] in kilometers
temp = [25 26 28 29 30 31 31 32 35 37 37] in degrees C
density = [2700 2700 2700 2750 2770 2770 2775 2780 2780 3000 3050] in kg/m3
viscosity = [100 110 120 130 140 150 160 170 180 190 200] Pascal*seconds

As you can see, the scales for each property along the x-axis are very different. Is this the kind of sample data you’re asking about? Here are some figures that are close to what I’m thinking:
http://www.ats-intl.com/expertise/images/geophysics-BG2.jpg
http://geophysics.eas.gatech.edu/people/anewman/classes/Geodynamics/misc/prem_earth.pdf

Your help is much appreciated, thanks!

Doug replied on : 22 of 49

@Zach,

I would say to use plotYYY, because that is close to what you want, but using depth as Y makes sense. Most user made files that do this focus on making Y the multi-axis.

I think you are best off looking at some of the existing ones for ideas on this, but you will have to write it yourself.

The added complication of 7 series, makes this much tougher.

Normalize all the values from zero to one. Plot them on the same axis. This gets you the qualitative comparison.

Take this a step further: When you click on a given series, the axis labels will change to be appropriate for that series. You would not be able to see all of them at once, but any one you wanted easy. Pretty clean interface, and not bad to implement.

What do you think?

Doug

Zach replied on : 23 of 49

Thanks for your suggestions Doug. I’ll give that a shot and see what happens. I’ve seen many of these kinds of plots with depth on the x-axis – perhaps for the same reason that you mentioned. I may end up plotting each individually and then using Illustrator to compile them all together on one figure (although I don’t like the idea of doing that – there should be an easy way!). In any case, I’ll let you know the outcome.

Thanks again.

Les replied on : 24 of 49

@Zach

This isn’t exactly what you are looking for but at least it puts all three parameters on the same page with aligned y (depth) axes.

subplot(1,3,1)
plot(temp, depth)
xlabel 'temp (deg C)'
ylabel 'depth (km)'
subplot(1,3,2)
plot(density, depth)
xlabel 'density (kg/m3)'
subplot(1,3,3)
plot(viscosity, depth)
xlabel 'viscosity (Pascal*sec)'

Zach replied on : 25 of 49

Hi Doug and Les,

I didn’t have a lot of time to mess with this, but I did find a work-around. I plotted all the figures as subplots side-by-side with the same scale on the y-axis. I consolidated them in the figure editor gui. It worked pretty well, but unfortunately isn’t repeatable like a script would be. A friend of a friend put together a pretty complicated script that seems to do everything without the subplot and figure editing. I’ll see if I can get permission to post it here for you to see.

Incidentally, the .eps outputs are pretty nice to work with in Illustrator. The plot can be ungrouped into all it’s component parts and manipulated. I ended up polishing up the figure with this in the end.

-Zach

Becky replied on : 26 of 49

I am having some issues with both plotyy and layerplot, which I assume is due to the fact that my two sets data have different numbers of points within the same x limits. It seems the x axes don’t stay locked together, but instead try to plot independently. Both data are in reference to time, one having many more points than the other, but if I ‘datetick’ the axis they become decoupled and won’t line up, instead seeming to create independent x axes. What am I doing wrong? The same issue happens when I try to use the function axis tight.

Doug replied on : 27 of 49

@Becky,

Doug

Amir replied on : 28 of 49

Hi Doug

The plotyy is generating normal axis for x axis, what should I write if I want to have both this right and left plotting feature AND a reverse log scale for x axis at the same time?

Thanks

Doug replied on : 29 of 49

@Amir,

Try this:


h = plotyy(rand(1,10),1000*rand(1,10),rand(1,10),rand(1,10))
set(h(1),'yscale','log')
set(h(1),'ydir','reverse')


David replied on : 30 of 49

Hi Doug,

I need to plot more than two axes on the Y axis. I can’t believe people don’t ask for such a thing. How would one extend the Y axis on the left farther left but keep the x axes in the same place? Does this make sense? For instance if you’ve already used plotyy but want to add a third axes. One could see the y axis farther left of the original but the x-axis would remain the same.

thanks,
David

Brian replied on : 32 of 49

Doug,

I’d like to re-ask Andrew’s question, #15. How do I alter the
right axes with the property editor gui? I’m generating plots
during program execution that users want to modify after the
program completes without command line stuff (so no returning
the AX value). I’ve tried this several times but it seems that I just can’t get the right-side axes properties. Alternatively, if I can’t do this, how can I get the AX value after the program completes?

Thanks.

Doug replied on : 33 of 49

@Brian,

What happened when your tried the solution I outlined?

You should store the AX value at the beginning if at all possible, that is the easiest time for this to happen. Have you tried looking for the children of the figure in question?

Doug

Abdulwehab replied on : 34 of 49

I have similar problem with Zach, I’m trying to plot around 5 different datas that all have a common x-axis. All datas have different values and scales. I want to plot each datas independently with different Y-axis one top over the others, but having common X- axis with the others. hope i will get and hear some tips from this valuable posts.

Oluwaseun Shonubi replied on : 36 of 49

NICe, pretty neat function!

Hanh replied on : 37 of 49

How can I plot multiple series on one y-axis (on the left) and another series on another y-axis (on the right)

Thanks!

Doug replied on : 38 of 49

@Hanh,

That is what this post was about.

Doug

Hanh replied on : 39 of 49

Could any one please give me a hint of how to plot y1, y2, y3 again x1, x2, x3 and shows 3 y-axes in the same figure. y1,y2,y3 and x1,x2,x3 are matrices. I have tried plotyyy and find out that the function works fine if x1,x2,x3 and y1,y2,y3 are vectors.

Thanks!

Doug replied on : 40 of 49

@Hanh,

If they are not vectors, what are they?

Doug

Hanh replied on : 41 of 49

x and y are mxn matirce

Doug replied on : 42 of 49

@Hanh,

If the function you want to use accepts vectors but not matrices, you should just pull out the vectors you want from the matrices you have.

Doug

Logan replied on : 43 of 49

Not sure if this is the right forum for this but…

I would like to re-ask part of Tobias’s question from two years ago, which didn’t seem to be fully answered:

“Is it possible to (easily) manipulate the zoom-function in PLOTYY-plots so that the y-axes gets updated when I zoom in? At the moment the axis-settings are very crude and they dont update, when I zoom in the window, so that I wont have any axis-ticks, when I zoom in deeply.”

I am having the same problem with the y-axes not updating when I zoom in deeply.

Steve L replied on : 44 of 49

Logan,

If your tick labels are the defaults, you can do this using the LINKAXES function.

If you have set special tick labels (say with the DATETICK function) then call ZOOM with an output argument. This output is the zoom mode object, and has several properties that you can use to control what happens before and after zooming occurs. The particular property in which you’d be most interested is the ActionPostCallback. As the name suggests, this callback is called after the axes are zoomed and allows you to do things like calling DATETICK to update the labels to reflect the new tick locations.

BP replied on : 45 of 49

Hello, I was wondering if someone could help me. I am trying to change the scale on my x axis, to simply magnify my results. I have two y axes using the plotyy and if I try to change the x axis limits, it only changes the numbers for the set of data on the left y axis. The x axis for the right side stays the same. I was not even aware they weren’t connected. For various reasons I have to do this after I run my code. I have been using the property editor, and I can’t seem to even select the x axis for the right set of data. Is there a way to group these? or a way to select the right axis to change it’s limits?
BP

Doug replied on : 46 of 49

@BP,

You can use XLIM. There are two axes there, be sure to use it on BOTH! Beware, the XLIMS are selected very carefully to line up. XLIM takes a vector of handles. You might you linkaxis too.

Doug

Meera replied on : 47 of 49

@BP

Hi, did you manage to work out how to change the x-axis limits for the right-hand side, or group both axes? I have the exact same problem and I can only edit my graph using the property editor.

Any help will be greatly appreciated. Thanks!

Meera

Jim Beck replied on : 48 of 49

When using plotyy, how is a label added to the right axis?
Thanks.
Jim

numan r replied on : 49 of 49

@Jim
use the set properties, sample as taken from Matlab Help Doc

figure
x = 0:0.01:20;
y1 = 200*exp(-0.05*x).*sin(x);
y2 = 0.8*exp(-0.5*x).*sin(10*x);
[AX,H1,H2] = plotyy(x,y1,x,y2,’plot’);

set(get(AX(1),’Ylabel’),’String’,’Slow Decay’)
set(get(AX(2),’Ylabel’),’String’,’Fast Decay’)

These postings are the author's and don't necessarily represent the opinions of MathWorks.