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Margaret Matocha
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Separated class file, updated examples
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‎adafruit_display_shapes/sparkline.py

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# class of sparklines in CircuitPython
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# created by Kevin Matocha - Copyright 2020 (C)
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# See the bottom for a code example using the `sparkline` Class.
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# # File: display_shapes_sparkline.py
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# A sparkline is a scrolling line graph, where any values added to sparkline using `add_value` are plotted.
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#
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# The `sparkline` class creates an element suitable for adding to the display using `display.show(mySparkline)`
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# or adding to a `displayio.Group` to be displayed.
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#
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# When creating the sparkline, identify the number of `max_items` that will be included in the graph.
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# When additional elements are added to the sparkline and the number of items has exceeded max_items,
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# any excess values are removed from the left of the graph, and new values are added to the right.
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import displayio
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from adafruit_display_shapes.line import Line
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class Sparkline(displayio.Group):
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def __init__(
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self,
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width,
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height,
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max_items,
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yMin=None, # None = autoscaling
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yMax=None, # None = autoscaling
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x=0,
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y=0,
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color=0xFFFFFF, # line color, default is WHITE
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):
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# define class instance variables
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self.width = width # in pixels
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self.height = height # in pixels
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self.color = color #
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self._max_items = max_items # maximum number of items in the list
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self._spark_list = [] # list containing the values
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self.yMin = yMin # minimum of y-axis (None: autoscale)
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self.yMax = yMax # maximum of y-axis (None: autoscale)
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self.yBottom = yMin # yBottom: The actual minimum value of the vertical scale, will be updated if autorange
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self.yTop = yMax # yTop: The actual minimum value of the vertical scale, will be updated if autorange
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self._x = x
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self._y = y
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super().__init__(
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max_size=self._max_items - 1, x=x, y=y
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) # self is a group of lines
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def add_value(self, value):
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if value is not None:
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if (
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len(self._spark_list) >= self._max_items
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): # if list is full, remove the first item
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self._spark_list.pop(0)
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self._spark_list.append(value)
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# self.update()
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@staticmethod
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def _xintercept(
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x1, y1, x2, y2, horizontalY
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): # finds intercept of the line and a horizontal line at horizontalY
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slope = (y2 - y1) / (x2 - x1)
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b = y1 - slope * x1
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if slope == 0 and y1 != horizontalY: # does not intercept horizontalY
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return None
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else:
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xint = (
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horizontalY - b
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) / slope # calculate the x-intercept at position y=horizontalY
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return int(xint)
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def _plotLine(self, x1, last_value, x2, value, yBottom, yTop):
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y2 = int(self.height * (yTop - value) / (yTop - yBottom))
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y1 = int(self.height * (yTop - last_value) / (yTop - yBottom))
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self.append(Line(x1, y1, x2, y2, self.color)) # plot the line
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def update(self):
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# What to do if there is 0 or 1 element?
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# get the y range
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if self.yMin == None:
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self.yBottom = min(self._spark_list)
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else:
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self.yBottom = self.yMin
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if self.yMax == None:
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self.yTop = max(self._spark_list)
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else:
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self.yTop = self.yMax
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if len(self._spark_list) > 2:
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xpitch = self.width / (
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len(self._spark_list) - 1
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) # this is a float, only make int when plotting the line
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for i in range(len(self)): # remove all items from the current group
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self.pop()
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for count, value in enumerate(self._spark_list):
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if count == 0:
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pass # don't draw anything for a first point
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else:
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x2 = int(xpitch * count)
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x1 = int(xpitch * (count - 1))
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# print("x1: {}, x2: {}".format(x1,x2))
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if (self.yBottom <= last_value <= self.yTop) and (
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self.yBottom <= value <= self.yTop
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): # both points are in range, plot the line
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self._plotLine(
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x1, last_value, x2, value, self.yBottom, self.yTop
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)
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else: # at least one point is out of range, clip one or both ends the line
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if ((last_value > self.yTop) and (value > self.yTop)) or (
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(last_value < self.yBottom) and (value < self.yBottom)
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):
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# both points are on the same side out of range: don't draw anything
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pass
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else:
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xintBottom = self._xintercept(
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x1, last_value, x2, value, self.yBottom
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) # get possible new x intercept points
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xintTop = self._xintercept(
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x1, last_value, x2, value, self.yTop
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) # on the top and bottom of range
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if (xintBottom is None) or (
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xintTop is None
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): # out of range doublecheck
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pass
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else:
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# Initialize the adjusted values as the baseline
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adj_x1 = x1
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adj_last_value = last_value
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adj_x2 = x2
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adj_value = value
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if value > last_value: # slope is positive
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if xintBottom >= x1: # bottom is clipped
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adj_x1 = xintBottom
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adj_last_value = self.yBottom # y1
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if xintTop <= x2: # top is clipped
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adj_x2 = xintTop
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adj_value = self.yTop # y2
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else: # slope is negative
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if xintTop >= x1: # top is clipped
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adj_x1 = xintTop
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adj_last_value = self.yTop # y1
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if xintBottom <= x2: # bottom is clipped
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adj_x2 = xintBottom
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adj_value = self.yBottom # y2
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self._plotLine(
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adj_x1,
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adj_last_value,
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adj_x2,
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adj_value,
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self.yBottom,
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self.yTop,
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)
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last_value = value # store value for the next iteration
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def values(self):
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return self._spark_list

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