Hi,
Is the current is constant over time? If not this becomes a harder problem
but not impossible -- you'd need to integrate the current curve to compute
the capacity labels.
I'm not sure if this is the best way to do it, but I made a dual axis for a
project (left/right wavelength and frequency axes) by copying/extending
AxisItem like this:
class AxisItemScaleFunction(pg.AxisItem):
"""Extension of pyqtgraph AxisItem which allows the axis tick labels to
be
transformed using a user-specified function.
Typical use would be to display the same axis data in two different unit
systems. For example, temperature in C and F, or light wavelength as
well as
photon energy.
Note that the axis range and scale is not changed, only the calculation
of
the axis tick labels."""
def __init__(self, orientation, pen=None, linkView=None, parent=None,
maxTickLength=-5, showValues=True, scalefunc=lambda x: x):
self.scalefunc = scalefunc
pg.AxisItem.__init__(self, orientation, pen=pen, linkView=linkView,
parent=parent, maxTickLength=maxTickLength, showValues=showValues)
def tickStrings(self, values, scale, spacing):
if self.logMode:
return self.logTickStrings(values, scale, spacing)
warnings.simplefilter("ignore")
try:
places = np.nanmax([0,
np.ceil(-np.log10((np.abs(self.scalefunc(values[0] + spacing
) - self.scalefunc(values[0])))*scale)),
np.ceil(-np.log10((np.abs(self.scalefunc(values[-1]) - self.
scalefunc(values[-1] - spacing)))*scale))])
except IndexError:
places = 0
warnings.simplefilter("default")
strings = []
for v in values:
vs = self.scalefunc(v) * scale
if abs(vs) < .001 or abs(vs) >= 10000:
vstr = "%g" % vs
else:
vstr = ("%%0.%df" % places) % vs
strings.append(vstr)
return strings
def updateAutoSIPrefix(self):
if self.label.isVisible():
(scale, prefix) = pg.siScale(max(abs(self.scalefunc(self.range[0
])), abs(self.scalefunc(self.range[1]))))
if self.labelUnits == '' and prefix in ['k', 'm']: ## If we
are not showing units, wait until 1e6 before scaling.
scale = 1.0
prefix = ''
self.setLabel(unitPrefix=prefix)
else:
scale = 1.0
self.autoSIPrefixScale = scale
self.picture = None
self.update()
def logTickStrings(self, values, scale, spacing):
return ["%0.1g"%x for x in 10 ** np.array(self.scalefunc(values)).
astype(float)]
In its init method it takes a reference to a function which is used to
compute the alternate tick labels. You then manually assign this custom
axis item to the plot when you create it, something like:
rax = AxisItemScaleFunction(orientation='right', scalefunc=lambda x: 1e-3*
constants.c/x if not x == 0 else np.inf)
self.spectrum = self.overview_graphicsLayoutWidget.addPlot(axisItems={
'right': rax})
self.spectrum.setLabels(left="Frequency (THz)", bottom="Intensity (a.u.)",
right="Wavelength (nm)")
self.spectrum_plot = self.spectrum.plot(pen=(255, 255, 0), name="Spectrum")
So if your current is constant, just sub your formula into the lambda
function above. If not, then you will probably want to create a full
function that integrates the current given a time t, and use
scalefunc=compute_capacity instead.
Hope that helps,
Patrick
On Thursday, 7 February 2019 21:41:24 UTC+10:30, [email protected]
wrote:
>
> BTW I forgot to mention I don't want to plot new curve, I just want one
> curve and 2 x-axes whose values are corresponds to each other
>
> W dniu czwartek, 7 lutego 2019 11:44:34 UTC+1 użytkownik
> [email protected] napisał:
>>
>> Hello. I have a program which gathers measurements of voltage, current
>> and time. I'd like to create a plot Voltage vs time and second X-axis at
>> top with Capacity on it. I've done simple window like this:
>>
>> import pyqtgraph as pg
>>
>> win=pg.GraphicsWindow("plot")
>> win.resize(1000,600)
>> plt=win.addPlot(row = 1, col = 0,title="Plot",labels={'left': 'Voltage
>> [V]','bottom': 'time [s]','top': 'Capacity [mAh]'})
>> curve=plt.plot(pen='b')
>> label_cords = pg.LabelItem(justify = "right")
>> So it looks like on screen attached.
>>
>> In my measurements I also get current so Capacity is calculated as:
>> current*10*time/36 (It's the same time I use to plot bottom x axis).
>>
>> How can I set values of top axis to show capacity corresponded to the
>> time on bottom axis?
>>
>> I've tried to work with one of
>>
>> plt.getAxis('top').setTickSpacing()
>>
>> plt.getAxis('top').setTicks()
>>
>> plt.getAxis('top').tickValues()
>>
>>
>>
>> but I don't really know how to set it properly. I want to keep autorange
>> function active (so when time axis going wider I want my Capacity axis to
>> expand aswell)
>>
>>
>>
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