pyqtgraph dateAxis

dateAxis.py

# dateAxis.py
# Usage: save dateAxis.py in directory with pyqtgraph py file
# Use sample code below to create plot with date axis
# from dateAxis import *
# daxis = DateAxis(orientation='bottom')
# flo = pg.PlotWidget(axisItems={'bottom': daxis, 'left': yaxis})
import time
import pyqtgraph as pg
import numpy as np
from pyqtgraph.Qt import QtGui, QtCore

def reduce(li, length):
    if len(li) <= length:
        return li
    r = int(len(li)/round(length,0))
    a = []
    i = 1
    for b in li:
        if i%r==0:
            a.append(b)
        i+=1
    return a

#override AxisItem class to handle dates
class DateAxis(pg.AxisItem):
    def tickStrings(self, values, scale, spacing):
        strns = []
        #if rng < 120:
        #    return pg.AxisItem.tickStrings(self, values, scale, spacing)
        if spacing < 3600*24: #less than 1 day
            string = '%H:%M'
        elif spacing >= 3600*24 and spacing < 3600*24*30: #1 day to 30 days
            string = "%d%b'%y"
        elif spacing >= 3600*24*30 and spacing < 3600*24*30*12: #30 days to 1 years
            string = "%b'%y"
        elif spacing >=3600*24*30*12: #more than 1 years
            string = '%Y'
        for x in values:
            try:
                strns.append(time.strftime(string, time.localtime(x)))
            except ValueError:  ## Windows can't handle dates before 1970
                strns.append('')
        return strns

    def tickValues(self, minVal, maxVal, size):
        '''
        Return the values and spacing of ticks to draw::
        
            [  
                (spacing, [major ticks]), 
                (spacing, [minor ticks]), 
                ... 
            ]
        '''
        minVal, maxVal = sorted((minVal, maxVal))
        span = maxVal - minVal

        minorTick = []
        if span < 3600*24*3: #less than 3 days
            minVal = round(minVal/900,0)*900 #900s = 15min
            maxVal = round(maxVal/900,0)*900
            for t in np.arange(minVal,maxVal,900):
                ti = time.localtime(t)
                if ti.tm_min == 0:
                    minorTick.append(t)
                    mnSp = 3600
        elif span >= 3600*24*3 and span < 3600*24*30*6: #3 days to 6 months
            minVal = round(minVal/(3600),0)*3600 #3600s = 1 hour
            maxVal = round(maxVal/(3600),0)*3600
            for t in np.arange(minVal,maxVal,3600):
                ti = time.localtime(t)
                if ti.tm_hour == 0:
                    minorTick.append(t)
                    mnSp = 3600*24
        elif span >= 3600*24*30*6 and span < 3600*24*30*36: #> 6 months to 3 years
            minVal = round(minVal/(3600*24),0)*3600*24 #3600*24s = 1 day
            maxVal = round(maxVal/(3600*24),0)*3600*24
            for t in np.arange(minVal,maxVal,3600*24):
                ti = time.localtime(t)
                if ti.tm_mday == 1:
                    minorTick.append(t)
                    mnSp = 3600*24*30
        elif span >= 3600*24*30*36: #over three years
            minVal = round(minVal/(3600*24),0)*3600*24 #3600*24s = 1 day
            maxVal = round(maxVal/(3600*24),0)*3600*24
            for t in np.arange(minVal,maxVal,3600*24):
                ti = time.localtime(t)
                if ti.tm_yday == 1:
                    minorTick.append(t)
                    mnSp = 3600*24*30
        minorTick = reduce(minorTick,12)
        if len(minorTick)>1:
            mnSp = minorTick[1]-minorTick[0]
        return [(mnSp,minorTick)]