Multiple Y Axis for single plot window

[Stefan H]

Hello,

Is there any possibilty to have multiple Y Axis for a PlotWidget containing different line graphs.

For e.g. I might have a live view showing a voltage and a current line plot. I want to add 2 axis to the left of the plot.

[Stefan H]

For e.g. how to generate a plot somehow like this: http://matplotlib.org/examples/axes_grid/demo_parasite_axes2.html ?

[Luke Campagnola]

This is possible, but it takes a little work. There is an earlier discussion of related issues here:

 https://groups.google.com/forum/#!msg/pyqtgraph/d2uqHW-mFxA/RoUgG2Ga3XIJ

And I've uploaded an example of adding an extra axis here:

http://bazaar.launchpad.net/~luke-campagnola/pyqtgraph/inp/view/head:/examples/MultiplePlotAxes.py

This will eventually become a built-in feature, but I don't have time to put it together at the moment.

Luke

[Stefan H]

Hi Luke,

Thanks a lot for your example, this was excactly what I was looking for. I switched to your development branche, because your example requires the signal "sigResized" which seems to be not present on the mainline.

Stefan

[Blot Romain]

Hi,

I simply put your example in a method "yyyAxisPlot" and I don't understand why the third axe is not display (see attached). Can you give me a hand please.

BTW : thanks for doing pyqtgraph. It is very useful.

Romain

[Luke Campagnola]

On Tue, Dec 10, 2013 at 9:55 AM, Blot Romain <blot....@gmail.com> wrote:

Hi,

I simply put your example in a method "yyyAxisPlot" and I don't understand why the third axe is not display (see attached). Can you give me a hand please.

Simple mistake: when adding an item to a layout, PyQt does not add a new reference to the item. Consequently, ax3 is collected as soon as yyyAxisPlot exits. An easy solution is just to add `pw.ax3 = ax3`.

 

[Blot Romain]

Works perfect! Thx

[Blot Romain]

Also, I try to add a legend with :

    #legends
    legend = pg.LegendItem()
    legend.setParentItem(pw.graphicsItem())
    legend.addItem(p1,"item 1")
    legend.addItem(p2,"item 1")
    legend.addItem(p3,"item 2")

but it is not working because of viewbox. Any idea?

Romain

[Luke Campagnola]

On Wednesday, December 11, 2013 7:29:09 AM UTC-5, Blot Romain wrote:

Also, I try to add a legend with :

    #legends
    legend = pg.LegendItem()
    legend.setParentItem(pw.graphicsItem())
    legend.addItem(p1,"item 1")
    legend.addItem(p2,"item 1")
    legend.addItem(p3,"item 2")

but it is not working because of viewbox. Any idea?

I do not understand--what is "not working" ? The following works as expected:

import pyqtgraph as pg

pw = pg.plot()

p1 = pw.plot([1,4,2,3], pen='r')

p2 = pw.plot([4,2,3,1], pen='g')

p3 = pw.plot([2,3,1,4], pen='b')

[Blot Romain]

Thanks for your answer.
This works for me too. But for my multiplotYaxes.py example (see attached above) I got this error :  
 
opts = self.item.opts
AttributeError: 'ViewBox' object has no attribute 'opts'

[Luke Campagnola]

On Wed, Dec 11, 2013 at 11:41 AM, Blot Romain <blot....@gmail.com> wrote:

Thanks for your answer.
This works for me too. But for my multiplotYaxes.py example (see attached above) I got this error :  
 
opts = self.item.opts
AttributeError: 'ViewBox' object has no attribute 'opts'

I see. The problem is that your p1, p2, p3 are PlotItems and ViewBoxes, whereas legend.addItem() requires a PlotCurveItem or PlotDataItem as its first argument.