On Thu, Jul 27, 2017 at 3:02 PM, Christopher Mullins <
[email protected]> wrote:
>
> (1) Question is what it sounds like. The situation is that I'm
> prototyping an EEG analysis application, and I'm trying to simulate the
> "Select bad channels" functionality in EEGLAB (a MATLAB GUI for this).
> This involves plotting sixty-something data channels together separated
> vertically, labeling the y-ticks with the name of each channel. When a
> user clicks a channel's data, the color should change (see minimal working
> example below).
>
> The trouble is it's easy to see that a certain channel of data is bad, but
> sometimes difficult to tell exactly which channel that is ie. the name of
> the channel. So I'd like to change the color of the tick label as well. Is
> there a way to specify just _one_ particular tick and change its color?
>
There is no way (currently) to specify the color of a single tick. However,
you could draw a new line (or anything else) on top. The easiest way to do
this is just to add a QGraphicsLineItem into the ViewBox.
If you expect the x range to change, then you might want the tick to
automatically set its x position/size like a tick. VTickGroup is one
example of how to do this (but it draws vertical ticks; it's meant for
marking event times). You could probably adapt that to draw a horizontal
tick instead.
Another option is to draw the tick outside the viewbox, but have it track
the vertical position of the ViewBox. Here's a simple example:
import pyqtgraph as pg
class Anchor(pg.ItemGroup):
"""Graphics item that anchors its position to the coordinate system
inside
a view box.
"""
def __init__(self, view, pos, x=True, y=True):
pg.ItemGroup.__init__(self)
self.view = view
self.anchorPos = pg.Point(pos)
self.anchorAxes = (x, y)
view.sigRangeChanged.connect(self.updatePosition)
def updatePosition(self):
pos = self.pos()
anchorPos =
self.parentItem().mapFromScene(self.view.mapViewToScene(self.anchorPos))
x, y = self.anchorAxes
if x:
pos.setX(anchorPos.x())
if y:
pos.setY(anchorPos.y())
self.setPos(pos)
plt = pg.plot()
# Anchor doesn't draw anything, it just tracks a position in the viewbox
anchor = Anchor(plt.plotItem.vb, [0, 0], x=False, y=True)
anchor.setParentItem(plt.plotItem)
# Attach any shape to the anchor
marker = pg.QtGui.QGraphicsEllipseItem(-10, -10, 20, 20)
marker.setPos(20, 0)
marker.setPen(pg.mkPen('y', width=3))
marker.setParentItem(anchor)
>
> Happy for any further suggestions on the code. Run it by pasting it into
> a file and running python -i filename.py.
>
> (2) If you look at the comment I've made in my code, I realized that in
> order for the sigClicked signal to fire, you need to use a PlotCurveItem
> (as in the MouseSelection.py example). If you use a PlotDataItem (which is
> returned from PlotItem.plot() [1]) the function connected to the sigClicked
> signal won't fire. Is this expected behavior, or a bug?
>
Thanks for the example. If you use a PlotDataItem, you can enable clicking
on the curve with `item.curve.setClickable(True)` (however, in your case a
PlotCurveItem is probably sufficient).
However, if you try to use `clickable=True` in the PlotDataItem
constructor, it is silently ignored. This is a bug.
Luke
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