VerticalLines

[Edmondo Giovannozzi]

I needed to plot hundreds of vertical lines corresponding to some transitions.

At the beginning I tried to use InfiniteLine but it was too slow. At the end I arrived at this solution that seems to work.

class plotVerticalLines(pg.PlotDataItem):

    

    def dataBounds(self, ax, frac=1.0, orthoRange=None):

        return [None, None]

    def setVerticalLines(self, x):

        

        x = np.vstack((x,x)).T.astype(float)

        y = np.zeros_like(x)

        vb = self.getViewBox()

        xr, yr = vb.viewRange()

        

        y[:,0] = yr[0]

        y[:,1] = yr[1]

        

        self.setData(x.ravel(), y.ravel(), connect='pairs')

        

        vb.sigYRangeChanged.connect(self._y_range_changed)

    

    def _y_range_changed(self, viewbox):

        xr, yr = viewbox.viewRange()

        # get the original not transfomed clipped etc.

        x = self.xData

        y = self.yData

        y[0::2] = yr[0]

        y[1::2] = yr[1]

        self.setData(x, y, connect='pairs')

Have you comment?

or way to improve it?

I really thanks the author of this really great library. I was able to get what I wanted with just few lines of code.

Cheers

[Oier Arcelus]

Hi!

I am having the same problem, everything about pyqtgraph is so fast. But I have the same problem. I have to plot several vertical lines, at different heights, using spans depending on the number of different levels I need to set.

It looks something like this 

for key, values in prf.reflections.items():
     span = ((float(key) - 1)/prf.nphase, float(key)/prf.nphase)

for val in values:
     line = pg.InfiniteLine(pos=val, angle=90, pen=self.pen8, span=span)
     self.ui_mainwindow.peaks_graph.addItem(line)

This is painfully slow so I am wondering if there is a better way.

[edmondo.g...@gmail.com]

The span is the fraction of the View (that in my previous case was all the View) that the line span. Even if you are zooming. But from what I see in your case it seems that it has instead a physical meaning not related to your view (I may be wrong of course).

In may case I reset the span whenever the view change (due for example to a zoom or a pan action by the user). It will be easy to add the span in the object itself then use the memorized span  to calculate the correct y position in the  _y_range_changed method.

Add an arguments to the setVerticalLines:

 def setVerticalLines(self, x, spans):

        self.spans = spans

In _range_changesd retrieve the spans (Assuming they are (n,2) matrices) and normalize them to the viewBox and set the y array.

Add also a check to test if the spans are defined like:

if not hasattr(self,'spans'):

    return 

y[0::2] = self.spans[:,0] * (yr[1] - yr[0]) + yr[0]

y[1::2] = self.spans[:,1] * (yr[1] - yr[0]) + yr[0]

If instead your y positions are fixed it will be even easier as you don't need a method that change them when the viewbox changes.

keys = prf.reflections.keys()

values = prf.reflections.values()

x =  np.vstack((values,values)).T.astype(float)

y = np.zeros_like(x)

y[:,0] = (float(keys) - 1)/prf.nphase

y[:,1] =  float(key)/prf.nphase

.....setData(x.ravel(), y.ravel(), connect='pairs')

or plot or which ever you prefer