|
| 1 | +""" |
| 2 | +================ |
| 3 | +Annotated Cursor |
| 4 | +================ |
| 5 | +
|
| 6 | +Display a data cursor including a text box, which shows the plot point close |
| 7 | +to the mouse pointer. |
| 8 | +
|
| 9 | +The new cursor inherits from `~matplotlib.widgets.Cursor` and demonstrates the |
| 10 | +creation of new widgets and their event callbacks. |
| 11 | +
|
| 12 | +See also the :doc:`cross hair cursor |
| 13 | +</gallery/misc/cursor_demo>`, which implements a cursor tracking the plotted |
| 14 | +data, but without using inheritance and without displaying the currently |
| 15 | +tracked coordinates. |
| 16 | +
|
| 17 | +.. note:: |
| 18 | + The figure related to this example does not show the cursor, because that |
| 19 | + figure is automatically created in a build queue, where the first mouse |
| 20 | + movement, which triggers the cursor creation, is missing. |
| 21 | +
|
| 22 | +""" |
| 23 | +from matplotlib.widgets import Cursor |
| 24 | +import numpy as np |
| 25 | +import matplotlib.pyplot as plt |
| 26 | + |
| 27 | + |
| 28 | +class AnnotatedCursor(Cursor): |
| 29 | + """ |
| 30 | + A crosshair cursor like `~matplotlib.widgets.Cursor` with a text showing \ |
| 31 | + the current coordinates. |
| 32 | +
|
| 33 | + For the cursor to remain responsive you must keep a reference to it. |
| 34 | + The data of the axis specified as *dataaxis* must be in ascending |
| 35 | + order. Otherwise, the `numpy.searchsorted` call might fail and the text |
| 36 | + disappears. You can satisfy the requirement by sorting the data you plot. |
| 37 | + Usually the data is already sorted (if it was created e.g. using |
| 38 | + `numpy.linspace`), but e.g. scatter plots might cause this problem. |
| 39 | + The cursor sticks to the plotted line. |
| 40 | +
|
| 41 | + Parameters |
| 42 | + ---------- |
| 43 | + line : `matplotlib.lines.Line2D` |
| 44 | + The plot line from which the data coordinates are displayed. |
| 45 | +
|
| 46 | + numberformat : `python format string <https://docs.python.org/3/\ |
| 47 | + library/string.html#formatstrings>`_, optional, default: "{0:.4g};{1:.4g}" |
| 48 | + The displayed text is created by calling *format()* on this string |
| 49 | + with the two coordinates. |
| 50 | +
|
| 51 | + offset : (float, float) default: (5, 5) |
| 52 | + The offset in display (pixel) coordinates of the text position |
| 53 | + relative to the cross hair. |
| 54 | +
|
| 55 | + dataaxis : {"x", "y"}, optional, default: "x" |
| 56 | + If "x" is specified, the vertical cursor line sticks to the mouse |
| 57 | + pointer. The horizontal cursor line sticks to *line* |
| 58 | + at that x value. The text shows the data coordinates of *line* |
| 59 | + at the pointed x value. If you specify "y", it works in the opposite |
| 60 | + manner. But: For the "y" value, where the mouse points to, there might |
| 61 | + be multiple matching x values, if the plotted function is not biunique. |
| 62 | + Cursor and text coordinate will always refer to only one x value. |
| 63 | + So if you use the parameter value "y", ensure that your function is |
| 64 | + biunique. |
| 65 | +
|
| 66 | + Other Parameters |
| 67 | + ---------------- |
| 68 | + textprops : `matplotlib.text` properties as dictionay |
| 69 | + Specifies the appearance of the rendered text object. |
| 70 | +
|
| 71 | + **cursorargs : `matplotlib.widgets.Cursor` properties |
| 72 | + Arguments passed to the internal `~matplotlib.widgets.Cursor` instance. |
| 73 | + The `matplotlib.axes.Axes` argument is mandatory! The parameter |
| 74 | + *useblit* can be set to *True* in order to achieve faster rendering. |
| 75 | +
|
| 76 | + """ |
| 77 | + |
| 78 | + def __init__(self, line, numberformat="{0:.4g};{1:.4g}", offset=(5, 5), |
| 79 | + dataaxis='x', textprops={}, **cursorargs): |
| 80 | + # The line object, for which the coordinates are displayed |
| 81 | + self.line = line |
| 82 | + # The format string, on which .format() is called for creating the text |
| 83 | + self.numberformat = numberformat |
| 84 | + # Text position offset |
| 85 | + self.offset = np.array(offset) |
| 86 | + # The axis in which the cursor position is looked up |
| 87 | + self.dataaxis = dataaxis |
| 88 | + |
| 89 | + # First call baseclass constructor. |
| 90 | + # Draws cursor and remembers background for blitting. |
| 91 | + # Saves ax as class attribute. |
| 92 | + super().__init__(**cursorargs) |
| 93 | + |
| 94 | + # Default value for position of text. |
| 95 | + self.set_position(self.line.get_xdata()[0], self.line.get_ydata()[0]) |
| 96 | + # Create invisible animated text |
| 97 | + self.text = self.ax.text( |
| 98 | + self.ax.get_xbound()[0], |
| 99 | + self.ax.get_ybound()[0], |
| 100 | + "0, 0", |
| 101 | + animated=bool(self.useblit), |
| 102 | + visible=False, **textprops) |
| 103 | + # The position at which the cursor was last drawn |
| 104 | + self.lastdrawnplotpoint = None |
| 105 | + |
| 106 | + def onmove(self, event): |
| 107 | + """ |
| 108 | + Overridden draw callback for cursor. Called when moving the mouse. |
| 109 | + """ |
| 110 | + |
| 111 | + # Leave method under the same conditions as in overridden method |
| 112 | + if self.ignore(event): |
| 113 | + self.lastdrawnplotpoint = None |
| 114 | + return |
| 115 | + if not self.canvas.widgetlock.available(self): |
| 116 | + self.lastdrawnplotpoint = None |
| 117 | + return |
| 118 | + |
| 119 | + # If the mouse left drawable area, we now make the text invisible. |
| 120 | + # Baseclass will redraw complete canvas after, which makes both text |
| 121 | + # and cursor disappear. |
| 122 | + if event.inaxes != self.ax: |
| 123 | + self.lastdrawnplotpoint = None |
| 124 | + self.text.set_visible(False) |
| 125 | + super().onmove(event) |
| 126 | + return |
| 127 | + |
| 128 | + # Get the coordinates, which should be displayed as text, |
| 129 | + # if the event coordinates are valid. |
| 130 | + plotpoint = None |
| 131 | + if event.xdata is not None and event.ydata is not None: |
| 132 | + # Get plot point related to current x position. |
| 133 | + # These coordinates are displayed in text. |
| 134 | + plotpoint = self.set_position(event.xdata, event.ydata) |
| 135 | + # Modify event, such that the cursor is displayed on the |
| 136 | + # plotted line, not at the mouse pointer, |
| 137 | + # if the returned plot point is valid |
| 138 | + if plotpoint is not None: |
| 139 | + event.xdata = plotpoint[0] |
| 140 | + event.ydata = plotpoint[1] |
| 141 | + |
| 142 | + # If the plotpoint is given, compare to last drawn plotpoint and |
| 143 | + # return if they are the same. |
| 144 | + # Skip even the call of the base class, because this would restore the |
| 145 | + # background, draw the cursor lines and would leave us the job to |
| 146 | + # re-draw the text. |
| 147 | + if plotpoint is not None and plotpoint == self.lastdrawnplotpoint: |
| 148 | + return |
| 149 | + |
| 150 | + # Baseclass redraws canvas and cursor. Due to blitting, |
| 151 | + # the added text is removed in this call, because the |
| 152 | + # background is redrawn. |
| 153 | + super().onmove(event) |
| 154 | + |
| 155 | + # Check if the display of text is still necessary. |
| 156 | + # If not, just return. |
| 157 | + # This behaviour is also cloned from the base class. |
| 158 | + if not self.get_active() or not self.visible: |
| 159 | + return |
| 160 | + |
| 161 | + # Draw the widget, if event coordinates are valid. |
| 162 | + if plotpoint is not None: |
| 163 | + # Update position and displayed text. |
| 164 | + # Position: Where the event occured. |
| 165 | + # Text: Determined by set_position() method earlier |
| 166 | + # Position is transformed to pixel coordinates, |
| 167 | + # an offset is added there and this is transformed back. |
| 168 | + temp = [event.xdata, event.ydata] |
| 169 | + temp = self.ax.transData.transform(temp) |
| 170 | + temp = temp + self.offset |
| 171 | + temp = self.ax.transData.inverted().transform(temp) |
| 172 | + self.text.set_position(temp) |
| 173 | + self.text.set_text(self.numberformat.format(*plotpoint)) |
| 174 | + self.text.set_visible(self.visible) |
| 175 | + |
| 176 | + # Tell base class, that we have drawn something. |
| 177 | + # Baseclass needs to know, that it needs to restore a clean |
| 178 | + # background, if the cursor leaves our figure context. |
| 179 | + self.needclear = True |
| 180 | + |
| 181 | + # Remember the recently drawn cursor position, so events for the |
| 182 | + # same position (mouse moves slightly between two plot points) |
| 183 | + # can be skipped |
| 184 | + self.lastdrawnplotpoint = plotpoint |
| 185 | + # otherwise, make text invisible |
| 186 | + else: |
| 187 | + self.text.set_visible(False) |
| 188 | + |
| 189 | + # Draw changes. Cannot use _update method of baseclass, |
| 190 | + # because it would first restore the background, which |
| 191 | + # is done already and is not necessary. |
| 192 | + if self.useblit: |
| 193 | + self.ax.draw_artist(self.text) |
| 194 | + self.canvas.blit(self.ax.bbox) |
| 195 | + else: |
| 196 | + # If blitting is deactivated, the overridden _update call made |
| 197 | + # by the base class immediately returned. |
| 198 | + # We still have to draw the changes. |
| 199 | + self.canvas.draw_idle() |
| 200 | + |
| 201 | + def set_position(self, xpos, ypos): |
| 202 | + """ |
| 203 | + Finds the coordinates, which have to be shown in text. |
| 204 | +
|
| 205 | + The behaviour depends on the *dataaxis* attribute. Function looks |
| 206 | + up the matching plot coordinate for the given mouse position. |
| 207 | +
|
| 208 | + Parameters |
| 209 | + ---------- |
| 210 | + xpos : float |
| 211 | + The current x position of the cursor in data coordinates. |
| 212 | + Important if *dataaxis* is set to 'x'. |
| 213 | + ypos : float |
| 214 | + The current y position of the cursor in data coordinates. |
| 215 | + Important if *dataaxis* is set to 'y'. |
| 216 | +
|
| 217 | + Returns |
| 218 | + ------- |
| 219 | + ret : {2D array-like, None} |
| 220 | + The coordinates which should be displayed. |
| 221 | + *None* is the fallback value. |
| 222 | + """ |
| 223 | + |
| 224 | + # Get plot line data |
| 225 | + xdata = self.line.get_xdata() |
| 226 | + ydata = self.line.get_ydata() |
| 227 | + |
| 228 | + # The dataaxis attribute decides, in which axis we look up which cursor |
| 229 | + # coordinate. |
| 230 | + if self.dataaxis == 'x': |
| 231 | + pos = xpos |
| 232 | + data = xdata |
| 233 | + lim = self.ax.get_xlim() |
| 234 | + elif self.dataaxis == 'y': |
| 235 | + pos = ypos |
| 236 | + data = ydata |
| 237 | + lim = self.ax.get_ylim() |
| 238 | + else: |
| 239 | + raise ValueError(f"The data axis specifier {self.dataaxis} should " |
| 240 | + f"be 'x' or 'y'") |
| 241 | + |
| 242 | + # If position is valid and in valid plot data range. |
| 243 | + if pos is not None and lim[0] <= pos <= lim[-1]: |
| 244 | + # Find closest x value in sorted x vector. |
| 245 | + # This requires the plotted data to be sorted. |
| 246 | + index = np.searchsorted(data, pos) |
| 247 | + # Return none, if this index is out of range. |
| 248 | + if index < 0 or index >= len(data): |
| 249 | + return None |
| 250 | + # Return plot point as tuple. |
| 251 | + return (xdata[index], ydata[index]) |
| 252 | + |
| 253 | + # Return none if there is no good related point for this x position. |
| 254 | + return None |
| 255 | + |
| 256 | + def clear(self, event): |
| 257 | + """ |
| 258 | + Overridden clear callback for cursor, called before drawing the figure. |
| 259 | + """ |
| 260 | + |
| 261 | + # The base class saves the clean background for blitting. |
| 262 | + # Text and cursor are invisible, |
| 263 | + # until the first mouse move event occurs. |
| 264 | + super().clear(event) |
| 265 | + if self.ignore(event): |
| 266 | + return |
| 267 | + self.text.set_visible(False) |
| 268 | + |
| 269 | + def _update(self): |
| 270 | + """ |
| 271 | + Overridden method for either blitting or drawing the widget canvas. |
| 272 | +
|
| 273 | + Passes call to base class if blitting is activated, only. |
| 274 | + In other cases, one draw_idle call is enough, which is placed |
| 275 | + explicitly in this class (see *onmove()*). |
| 276 | + In that case, `~matplotlib.widgets.Cursor` is not supposed to draw |
| 277 | + something using this method. |
| 278 | + """ |
| 279 | + |
| 280 | + if self.useblit: |
| 281 | + super()._update() |
| 282 | + |
| 283 | + |
| 284 | +fig, ax = plt.subplots(figsize=(8, 6)) |
| 285 | +ax.set_title("Cursor Tracking x Position") |
| 286 | + |
| 287 | +x = np.linspace(-5, 5, 1000) |
| 288 | +y = x**2 |
| 289 | + |
| 290 | +line, = ax.plot(x, y) |
| 291 | +ax.set_xlim(-5, 5) |
| 292 | +ax.set_ylim(0, 25) |
| 293 | + |
| 294 | +# A minimum call |
| 295 | +# Set useblit=True on most backends for enhanced performance |
| 296 | +# and pass the ax parameter to the Cursor base class. |
| 297 | +# cursor = AnnotatedCursor(line=lin[0], ax=ax, useblit=True) |
| 298 | + |
| 299 | +# A more advanced call. Properties for text and lines are passed. |
| 300 | +# Watch the passed color names and the color of cursor line and text, to |
| 301 | +# relate the passed options to graphical elements. |
| 302 | +# The dataaxis parameter is still the default. |
| 303 | +cursor = AnnotatedCursor( |
| 304 | + line=line, |
| 305 | + numberformat="{0:.2f}\n{1:.2f}", |
| 306 | + dataaxis='x', offset=[10, 10], |
| 307 | + textprops={'color': 'blue', 'fontweight': 'bold'}, |
| 308 | + ax=ax, |
| 309 | + useblit=True, |
| 310 | + color='red', |
| 311 | + linewidth=2) |
| 312 | + |
| 313 | +plt.show() |
| 314 | + |
| 315 | +############################################################################### |
| 316 | +# Trouble with non-biunique functions |
| 317 | +# ----------------------------------- |
| 318 | +# A call demonstrating problems with the *dataaxis=y* parameter. |
| 319 | +# The text now looks up the matching x value for the current cursor y position |
| 320 | +# instead of vice versa. Hover your cursor to y=4. There are two x values |
| 321 | +# producing this y value: -2 and 2. The function is only unique, |
| 322 | +# but not biunique. Only one value is shown in the text. |
| 323 | + |
| 324 | +fig, ax = plt.subplots(figsize=(8, 6)) |
| 325 | +ax.set_title("Cursor Tracking y Position") |
| 326 | + |
| 327 | +line, = ax.plot(x, y) |
| 328 | +ax.set_xlim(-5, 5) |
| 329 | +ax.set_ylim(0, 25) |
| 330 | + |
| 331 | +cursor = AnnotatedCursor( |
| 332 | + line=line, |
| 333 | + numberformat="{0:.2f}\n{1:.2f}", |
| 334 | + dataaxis='y', offset=[10, 10], |
| 335 | + textprops={'color': 'blue', 'fontweight': 'bold'}, |
| 336 | + ax=ax, |
| 337 | + useblit=True, |
| 338 | + color='red', linewidth=2) |
| 339 | + |
| 340 | +plt.show() |
0 commit comments