legend for plotyy causes axes problem

Hello!

Can anyone help me?

The legend in my plot generated by plotyy causes a displacement of one y-axis.

Does anyone knows a solution? Thanks

 x = 1:100;
 y1= randn(1,length(x));
 y2= randn(1,length(x));
 y3= randn(1,length(x));
 y4= randn(1,length(x));

 % plot1
    [hA,h1,h2] = plotyy(x,y1,x,y2);
    hold on
 % plot2
    [hB,h3,h4] = plotyy(x,y3,x,y4);

 hold off
 legend([h1,h2,h3,h4],'a','b','c','d','location','northoutside','orientation','horizontal')
 refresh

Answer 1

[dpb]

There are multiple axes created by plotyy and hold operates on only one at a time (and, disappointingly, won't accept a vector of multiple handles). Then, on top of that, when you use plotyy a second time you end up creating yet a third axis...

After executing your plotting calls--

>> [hA; hB]  % look at axes handles...
ans =
173.0382  175.0382
173.0382  180.0382
>>

Note the LH axes was plotted into with the second call but a second RH axis was created. So, now you've got three to try to synchronize if you do that. So, "don't DO that!!!" :)

Instead,

>> [hA,h1,h2] = plotyy(x,y1,x,y2);  % first call to create the two axes
>> set(hA,'nextplot','add')         % "hold on" for multiple axes
>> h3 = plot(hA(1),x,y3);           % add to the LH axis
>> h4 = plot(hA(2),x,y4);           % and to the RH one as well
>> legend([h1,h2,h3,h4],'a','b','c','d','location','northoutside','orientation','horizontal')
>>

Now axes will be in synch and both reduced to place the legend as desired.

[Tom Georgi]

It works great :)

Many thanks!

[dpb]

You're welcome, of course...I discovered this quirk some time ago that plotyy creates that second RH axis but keeps the same LH one. I think this is a bug and submitted it some time ago as such.

I believe, like subplot, plotyy should recognize both axes overlap identically existing ones and use them instead of creating the third. I suspect nobody at TMW envisioned calling plotyy with hold on and so the design/implementation doesn't take it into account.