blog:2022:0518_cryptoview_restoring_chart_panel [NervTech's Wiki]

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====== Cryptoview: Restoring the charts panel ======

{{tag>dev python cryptoview}}

So, continuing the work started in [[blog:2022:0517_cryptoview_restoring_overview_panel|my previous article]] on this topic, I'm now going to restore the "chart panel", which was used to display 4 charts of the selected coin with 4 different time frames. As in the initial version I will use matplotlib to draw the chart. And in fact, I've already been trying to integrate that package with pyqt5 and it works just fine, so this task here should not be too hard hopefully ;-). Let's get started!

====== ======

===== Initial ChartPanel construction =====

  * As reference, here is the type of display we want to replicate [//Or well, with a bit more data in it...//]

{{ blog:2022:0518:old_monitored_panel.png }}

  * So, let's start a new **ChartPanel** widget: <sxh python; highlight: []>"""ChartPanel widget module"""

import logging
from PyQt5 import QtCore
from PyQt5.QtCore import Qt
import PyQt5.QtWidgets as qwd

from nvp.nvp_context import NVPContext
from nvh.app.cryptoview.coin_panel import CoinPanel
from nvh.app.cryptoview.price_manager import PriceManager

logger = logging.getLogger(__name__)


class ChartPanel(qwd.QWidget):
    """ChartPanel class"""

    def __init__(self):
        """Constructor of the ChartPanel class"""
        super().__init__()

        # Create a CoinGecko() instance:
        ctx = NVPContext.get()
        self.pman: PriceManager = ctx.get_component("price_manager")
        self.pman.on_coins_data_updated(self.update_coin_panels)
        self.coin_panels = {}
        self.selected_panel = None
        self.build_panel()

        setattr(self, "sizeHint", lambda: QtCore.QSize(360, 300))

    def build_panel(self):
        """Build the panel for this widget"""

        lyt = qwd.QHBoxLayout()
        lyt.setContentsMargins(5, 5, 5, 5)
        lyt.setSpacing(5)

        col = qwd.QVBoxLayout()
        col.setContentsMargins(0, 0, 0, 0)
        col.setSpacing(5)

        coins = self.pman.get_monitored_coins()

        panel = qwd.QWidget()
        # panel.setSizePolicy(qwd.QSizePolicy.MinimumExpanding,
        #                     qwd.QSizePolicy.MinimumExpanding)

        col2 = qwd.QVBoxLayout()
        col2.setContentsMargins(5, 5, 5, 5)
        col2.setSpacing(5)

        for cid, coin in coins.items():
            cpanel = CoinPanel(coin)
            cpanel.on_click(self.on_coin_panel_clicked)
            self.coin_panels[cid] = cpanel
            col2.addWidget(cpanel, stretch=0)

        panel.setLayout(col2)
        # QtCore.QTimer.singleShot(0, panel.adjustSize)

        scroll = qwd.QScrollArea()
        # scroll.setStyleSheet("QScrollArea { border: none; }")
        scroll.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOn)
        scroll.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        scroll.setWidget(panel)
        scroll.setWidgetResizable(True)

        # QtCore.QTimer.singleShot(0, scroll.adjustSize)
        col.addWidget(scroll)
        lyt.addLayout(col)
        lyt.addStretch(1)

        self.setLayout(lyt)

        # Select bitcoin by default:
        self.selected_panel = self.coin_panels['bitcoin']
        self.selected_panel.highlight(True)

    def update_coin_panels(self):
        """Update the coins panels using the coins data from the price manager"""

        alldata = self.pman.get_coins_data()
        for cname, panel in self.coin_panels.items():
            if cname not in alldata:
                logger.warning("No data available for coin %s", cname)
                continue

            cdata = alldata[cname]
            panel.set_price(cdata["price"])
            panel.set_quote_symbol(cdata["quote_symbol"])
            panel.set_percent_change(cdata["percent_change"])
            panel.set_percent_ratio(cdata["percent_ratio"])
            panel.update()

        logger.info("Done updating coin panels on ChartPanel")

    def on_coin_panel_clicked(self, panel, _event):
        """Event when a given panel is clicked."""
        if self.selected_panel == panel:
            # Nothing to change
            return

        if self.selected_panel is not None:
            self.selected_panel.highlight(False)

        logger.info("Selecting coin %s", panel.get_symbol())
        self.selected_panel = panel
        self.selected_panel.highlight(True)
</sxh>

  * The initial version above will only build the scrollable list of monitored coins,
  * But this list is already re-using the CoinPanel class,
  * And I added support to select/highlight one of those panels with a simple mouse click event.
  * => Next I should add the 4 plots.

===== Adding the 4 plots display =====

  * Here is the main section added to create the plots in tbe **build_panel** method: <sxh python; highlight: []>        # Adding the plots here:
        chart_col = qwd.QVBoxLayout()
        chart_col.setContentsMargins(0, 0, 0, 0)
        chart_col.setSpacing(5)
        lyt.addLayout(chart_col, stretch=1)

        row = qwd.QHBoxLayout()
        row.setContentsMargins(0, 0, 0, 0)
        row.setSpacing(5)
        chart_col.addLayout(row)

        def create_chart(layout):
            clyt = qwd.QVBoxLayout()
            clyt.setContentsMargins(0, 0, 0, 0)

            chart = PlotCanvas(self, width=2, height=2, dpi=100)
            toolbar = chart.create_toolbar(self)

            clyt.addWidget(toolbar)
            clyt.addWidget(chart)
            layout.addLayout(clyt)
            self.charts.append(chart)

        create_chart(row)  # chart 0
        create_chart(row)  # chart 1

        row = qwd.QHBoxLayout()
        row.setContentsMargins(0, 0, 0, 0)
        row.setSpacing(5)
        chart_col.addLayout(row)

        create_chart(row)  # chart 2
        create_chart(row)  # chart 3

        self.setLayout(lyt)

        # Select bitcoin by default:
        self.selected_panel = self.coin_panels['bitcoin']
        self.selected_panel.highlight(True)</sxh>

  * Note that above I'm using a dedicated class **PlotCanvas** to encapsulate the matplotlib plot: <sxh python; highlight: []>"""matplotlib canvas module"""

import logging
import matplotlib

from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg, NavigationToolbar2QT as NavigationToolbar
from matplotlib.figure import Figure

matplotlib.use('Qt5Agg')

logger = logging.getLogger(__name__)


class PlotCanvas(FigureCanvasQTAgg):
    """Helper class to display a single matplotlib figure"""

    def __init__(self, _parent=None, width=5, height=4, dpi=100):
        fig = Figure(figsize=(width, height), dpi=dpi)
        self.axes = fig.add_subplot(111)
        super(PlotCanvas, self).__init__(fig)

    def create_toolbar(self, parent):
        """Create a matplotlib toolbar for this canvas"""
        return NavigationToolbar(self, parent)
</sxh>

  * And with that I get the following display: 

{{ blog:2022:0518:initial_charts.png }}


===== Displaying graphs on the plots =====

  * I had to inject some non-trivial code to support drawing the charts, the biggest part of if being in the **ChartPanel** class: <sxh python; highlight: []>    def set_plot_data(self, plot, title, prices, vols, times):
        """Assign the data to a given PlotWidget"""

        # logDEBUG("Dates: %s" % xx[:10])
        plot.chart.clear()
        plot.chart.set_title(title)
        if prices.size == 0:
            logger.warning("No price data for '%s'", title)

        plot.draw(prices, vols, times)

    def load_price_charts(self, coin_id):
        """Load the price charts for a given coin."""

        # Retrieve the coin from the panel:
        coin = self.coin_panels[coin_id].get_coin()
        sym = coin.symbol().upper()

        # get the quote from the price manager:
        quote = self.pman.get_quote_coin()

        # Build the 24h/7days charts from the highres data:
        price_data = self.pman.get_price_data()

        hres = price_data[coin_id]['highres']
        hist = price_data[coin_id]['history']
        qhres = None if quote is None else price_data[quote]['highres']
        qhist = None if quote is None else price_data[quote]['history']

        # get the current timestamp:
        now_ts = self.pman.get_timestamp()

        def get_data(dset, start_ts):
            """Retrieve the data from a dataset, starting from a given timestamp"""
            data = dset[dset[:, 0] >= start_ts, :]

            # Check if we actually had more data before that and otherwise assume this was the start of the currency:
            if dset[0, 0] > start_ts+1:
                arr = np.empty((2, data.shape[1]), dtype=np.float)
                arr[:] = np.nan
                arr[0, 0] = start_ts
                arr[1, 0] = dset[0, 0]-1
                data = np.vstack([arr, data])
            return data

        def draw_chart(chart_idx, dset, quote_dset, start_ts, title):
            """Draw a given chart by index"""
            data = get_data(dset, start_ts)
            prices = None
            if quote is None:
                prices = data[:, 1]
            elif quote.get_id() == "bitcoin":
                prices = data[:, 4]
            elif quote.get_id() == "ethereum":
                prices = data[:, 5]
            else:
                # Get the quote data from that start timestamp:
                qdata = get_data(quote_dset, start_ts)

                # we might not have the same number of entries, but in that case we simply interpolate the quote on the
                # current timestamps:
                qprices = np.interp(data[:, 0].astype(float), qdata[:, 0].astype(float), qdata[:, 1].astype(float))

                bprices = data[:, 1]

                # Then we do the division:
                prices = bprices / qprices

            vols = data[:, 3]
            times = data[:, 0].astype(np.int64)
            times = np.datetime64('1970-01-01T00:00:00') + times.astype('timedelta64[ms]')

            self.set_plot_data(self.charts[chart_idx], title, prices, vols, times)

        qstr = "USD" if quote is None else quote.symbol().upper()

        # 24H chart:
        draw_chart(0, hres, qhres, now_ts - 24*3600, f"{sym} - 24h [{qstr}]")

        # 7 days chart:
        draw_chart(1, hres, qhres, now_ts - 7*24*3600, f"{sym} - 7 Days [{qstr}]")

        # 30 days chart:
        # To draw the history charts we should also include the newest data from the high res datasets:
        last_hist_ts = hist[-1, 0]
        # Select all entries newer than the "last_hist_ts" from the high res dataset:
        append_hres = hres[hres[:, 0] > last_hist_ts, :]

        hist = np.vstack([hist, append_hres])
        if qhist is not None:
            assert qhist[-1, 0] == last_hist_ts, f"Mismatch in last history timestamp: {qhist[-1, 0]} != {last_hist_ts}"
            append_hres2 = qhres[qhres[:, 0] > last_hist_ts, :]
            len1 = len(append_hres)
            len2 = len(append_hres2)
            assert len1 == len2, f"Mismatch in apendHRes length: {len1} != {len2}"
            qhist = np.vstack([hist, append_hres2])

        draw_chart(2, hist, qhist, now_ts - 30*24*3600, f"{sym} - 30 Days [{qstr}]")

        # Max Days chat:
        max_days = coin.get_num_days()

        dset = hist if max_days > 7 else hres
        qds = qhist if max_days > 7 else qhres
        draw_chart(3, dset, qds, now_ts - max_days*24*3600, f"{sym} - Max ({max_days} Days) [{qstr}]")

</sxh>

  * In the process I also added an additional level of indirection when building the PlotCanvas objects: these are now encapsulated in a **PlotWidget** class specific to my CryptoView project: <sxh python; highlight: []>"""PlotWidget widget module"""

import logging
import PyQt5.QtWidgets as qwd
import numpy as np

from nvh.gui.plot_canvas import PlotCanvas

logger = logging.getLogger(__name__)


class PlotWidget(qwd.QFrame):
    """PlotWidget class"""

    def __init__(self):
        """Constructor of the PlotWidget class"""
        super().__init__()

        lyt = qwd.QVBoxLayout()
        lyt.setContentsMargins(0, 0, 0, 0)

        self.chart = PlotCanvas(self, width=2, height=2, dpi=100)
        self.toolbar = self.chart.create_toolbar(self)

        lyt.addWidget(self.toolbar)
        lyt.addWidget(self.chart)

        self.setLayout(lyt)

    def draw(self, prices, vols, xpos, allow_nan=True):
        """Draw price and volume data."""
        if prices.size == 0:
            self.chart.axes.text(0.5, 0.5, "No price data.", size="large", ha='center', va='center', weight='demi')
            return

        assert prices.size > 0, "Invalid prices array"
        if xpos is None:
            xpos = np.arange(prices.size)

        prices = prices.astype(np.float)
        vols = vols.astype(np.float)

        if not allow_nan:
            np.nan_to_num(prices, copy=False)
            np.nan_to_num(vols, copy=False)
            assert not np.isnan(prices).any(), "Should not have nan price values here!"

        pmin = np.nanmin(prices)
        pmax = np.nanmax(prices)

        # Rescale the volume prices in 1/5 of the price range:
        vrange = (pmax-pmin)/5.0
        vmin = np.nanmin(vols)
        vmax = np.nanmax(vols)

        vscale = (vrange/(vmax - vmin)) if vmax > vmin else 1.0
        vols = (vols-vmin)*vscale + pmin-vrange

        # draw a white line to ensure we have all the xx raneg covered even with Nan values:
        dum = np.ones((xpos.size))*pmin

        self.chart.axes.plot(xpos, dum, color='white', linewidth=1)
        self.chart.axes.plot(xpos, prices, color='blue', linewidth=1)
        self.chart.axes.plot(xpos, vols, color='red', linewidth=1)

        self.chart.draw()
</sxh>

  * And with that, here is a the kind of display I get:

{{ blog:2022:0518:charts_with_plot.png }}

  * **Note**: Selecting a different coin in the left panel will of course also change the chart content since I added: <sxh python; highlight: []>    def on_coin_panel_clicked(self, panel, _event):
        """Event when a given panel is clicked."""
        if self.selected_panel == panel:
            # Nothing to change
            return

        if self.selected_panel is not None:
            self.selected_panel.highlight(False)

        logger.info("Selecting coin %s", panel.get_symbol())
        self.selected_panel = panel
        self.selected_panel.highlight(True)

        self.update_charts()

    def update_charts(self):
        """Should update the charts here."""
        coin = self.selected_panel.get_coin()
        self.load_price_charts(coin.get_id())       
</sxh>

  * One last thing I think I should change already on this display is the date values on the X axis: these are currently completely messed up 😀

  * => And here we go:

{{ blog:2022:0518:charts_xlabels.png }}

  * To fix the xlabels above, I converted the "times" values as seconds from the current timestamp: <sxh python; highlight: []>            times = data[:, 0].astype(np.int64)

            # times = np.datetime64('1970-01-01T00:00:00') + times.astype('timedelta64[ms]')
            # use the current timestamp as reference:
            times = now_ts - times

            self.set_plot_data(self.charts[chart_idx], title, prices, vols, times)</sxh>

  * And on construction of the **PlotWidget** objects, I provide a "period" value (in number of seconds): <sxh python; highlight: []>        wid = PlotWidget(3600)
        row.addWidget(wid)
        self.charts.append(wid)
        wid = PlotWidget(3600*24)
        row.addWidget(wid)
        self.charts.append(wid)</sxh>

  * Then I use that period, and an automatic "offset" value to define the range of my xlabels on each plot (and inverting that range in the process): <sxh python; highlight: []>        # xpos are times given in seconds from current timestamp, so we rescale given our period:
        # This is given in seconds, so we convert that to hours or days, or weeks depending on the number of entries:
        xpos = xpos.astype(np.float32) / self.period
        
        xmin = np.amin(xpos)
        xmax = np.amax(xpos)
        offset = self.offset * (xmax - xmin)

        self.chart.axes.set_xlim([xmax+offset, xmin-offset])</sxh>
    
  * => So in effect, I display an **hour resolution** for the day chart, a **day resolution** for the week and month charts, and a **month resolution** for the full duration chart.

===== Conclusion =====

  * As usual, to try to keep this article not too long I will stop here for this time,
  * Next time, I should add support to double-click on a ConiWidget from the Overview panel to get the charts in the Charts panel (and vice versa)
  * And also extract the "toolbar" from the overview panel as a dedicated toolbar in the app so that I could also change the quote coin when looking at the charts directly ;-)