Hey, I've tried replicating the suggestions but cant seem to get anything
to appear, I wrote the script below and ran it from the windows command
prompt using Python. I'm using numpy 1.14, pyqt 5.9 and pyqtgraph 0.10.
When I just use the code suggested by Samuel Palato nothing gets displayed
either. I've also tried running this in a jupyter notebook but to no avail.
import numpy as np
import pyqtgraph as pg
from pyqtgraph.Qt import QtGui, QtCore
class IndexedAxis(pg.AxisItem):
"""
Axis where pixels are mapped using a numpy array
"""
def __init__(self, orientation, mapping=None, **kw):
super(IndexedAxis, self).__init__(orientation, **kw)
self.mapping = mapping
self.fmt = "{:.02f}"
def tickStrings(self, values, scale, spacing):
if self.mapping is None:
return super(IndexedAxis, self).tickStrings(values, scale,
spacing)
# count values smaller than 0
labels = []
idx = np.array(values, dtype=np.int)-1
left_pad = np.count_nonzero(idx < 0)
right_pad = np.count_nonzero(idx >= self.mapping.size)
idx = np.compress(np.logical_and(idx>=0, idx< self.mapping.size),
idx)
labels.extend([""]*left_pad)
labels.extend([self.fmt.format(v) for v in self.mapping[idx]])
labels.extend([""]*right_pad)
return labels
app = QtGui.QApplication([])
mw = QtGui.QMainWindow
view = pg.GraphicsLayoutWidget()
w1 = view.addPlot()
x_values = np.linspace(-100, 100)
mapped_axis = IndexedAxis('bottom', mapping=x_values)
plot_item = pg.PlotItem(axisItems={'bottom': mapped_axis})
image_item =pg.ImageItem()
plot_item.addItem(image_item)
w1.addItem(plot_item)
On Tuesday, April 19, 2016 at 6:50:05 PM UTC+1, Samuel Palato wrote:
>
> Hi,
>
> I managed to do something similar.
>
> My data has x and y axes with almost constant spacing, so I'm ok with even
> sized pixels on display. However, the x and y axes display custom values,
> looked up from the corresponding arrays. This is a bit closer to the
> behavior of `matplotlib.imshow` with the `extent` keyword.
>
> The trick is to subclass `AxisItem` in order to display custom tick
> labels. See:
> https://bitbucket.org/snippets/spalato/X6nL4/indexed-axis#file-IndexedAxis.py
> You then need to create the axis items and pass them to the PlotItem your
> ImageItem is going to reside in:
> x_values = np.linspace(-100, 100, n=51)
> mapped_axis = IndexedAxis('bottom', mapping=x_values)
> plot_item = pg.PlotItem(axisItems={'bottom': mapped_axis})
> image_item =pg.ImageItem()
> plot_item.addItem(image_item)
> Or something similar.
> To update the axis values, you need to update the axis' `mapping`
> attribute to the new values.
>
> So far, this works, but I get an extra set of axes in the top right
> corner. (which brought me here...)
>
> If constant pixels are unacceptable, you could try creating a display
> image using nearest interpolation, and plotting the resulting image using
> the technique described above.
>
> Hope this helps,
> Samuel Palato
>
>
> On Thursday, 17 March 2016 09:37:17 UTC-4, Nicola Creati wrote:
>>
>> Hello,
>> I'm trying to move from Matplotlib to PyQtGraph but I need something
>> equivalent to the Matplotlib pcolormesh/pcolor command that accepts X, Y
>> and C as input. *X* and *Y *specify the (*x*, *y*) coordinates of the
>> colored quadrilaterals and C is the array of values. Can I get the same
>> with PyQtGraph, please?
>> Thanks.
>>
>> Nicola
>>
>
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