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"""
Place a legend on the axes at location loc. Labels are a
sequence of strings and loc can be a string or an integer
specifying the legend location
The location codes are
'best' : 0, (only implemented for axis legends)
'upper right' : 1,
'upper left' : 2,
'lower left' : 3,
'lower right' : 4,
'right' : 5,
'center left' : 6,
'center right' : 7,
'lower center' : 8,
'upper center' : 9,
'center' : 10,
Return value is a sequence of text, line instances that make
up the legend
"""
from __future__ import division
import warnings
import numpy as np
from matplotlib import rcParams
from matplotlib.artist import Artist, allow_rasterization
from matplotlib.cbook import is_string_like, iterable, silent_list, safezip
from matplotlib.font_manager import FontProperties
from matplotlib.lines import Line2D
from matplotlib.patches import Patch, Rectangle, Shadow, FancyBboxPatch
from matplotlib.collections import LineCollection, RegularPolyCollection, \
CircleCollection
from matplotlib.transforms import Bbox, BboxBase, TransformedBbox, BboxTransformTo
from matplotlib.offsetbox import HPacker, VPacker, TextArea, DrawingArea
class Legend(Artist):
"""
Place a legend on the axes at location loc. Labels are a
sequence of strings and loc can be a string or an integer
specifying the legend location
The location codes are::
'best' : 0, (only implemented for axis legends)
'upper right' : 1,
'upper left' : 2,
'lower left' : 3,
'lower right' : 4,
'right' : 5,
'center left' : 6,
'center right' : 7,
'lower center' : 8,
'upper center' : 9,
'center' : 10,
loc can be a tuple of the noramilzed coordinate values with
respect its parent.
Return value is a sequence of text, line instances that make
up the legend
"""
codes = {'best' : 0, # only implemented for axis legends
'upper right' : 1,
'upper left' : 2,
'lower left' : 3,
'lower right' : 4,
'right' : 5,
'center left' : 6,
'center right' : 7,
'lower center' : 8,
'upper center' : 9,
'center' : 10,
}
zorder = 5
def __str__(self):
return "Legend"
def __init__(self, parent, handles, labels,
loc = None,
numpoints = None, # the number of points in the legend line
markerscale = None, # the relative size of legend markers vs. original
scatterpoints = 3, # TODO: may be an rcParam
scatteryoffsets=None,
prop = None, # properties for the legend texts
# the following dimensions are in axes coords
pad = None, # deprecated; use borderpad
labelsep = None, # deprecated; use labelspacing
handlelen = None, # deprecated; use handlelength
handletextsep = None, # deprecated; use handletextpad
axespad = None, # deprecated; use borderaxespad
# spacing & pad defined as a fraction of the font-size
borderpad = None, # the whitespace inside the legend border
labelspacing=None, #the vertical space between the legend entries
handlelength=None, # the length of the legend handles
handletextpad=None, # the pad between the legend handle and text
borderaxespad=None, # the pad between the axes and legend border
columnspacing=None, # spacing between columns
ncol=1, # number of columns
mode=None, # mode for horizontal distribution of columns. None, "expand"
fancybox=None, # True use a fancy box, false use a rounded box, none use rc
shadow = None,
title = None, # set a title for the legend
bbox_to_anchor = None, # bbox that the legend will be anchored.
bbox_transform = None, # transform for the bbox
):
"""
- *parent* : the artist that contains the legend
- *handles* : a list of artists (lines, patches) to add to the legend
- *labels* : a list of strings to label the legend
Optional keyword arguments:
================ ==================================================================
Keyword Description
================ ==================================================================
loc a location code
prop the font property
markerscale the relative size of legend markers vs. original
numpoints the number of points in the legend for line
scatterpoints the number of points in the legend for scatter plot
scatteryoffsets a list of yoffsets for scatter symbols in legend
fancybox if True, draw a frame with a round fancybox. If None, use rc
shadow if True, draw a shadow behind legend
ncol number of columns
borderpad the fractional whitespace inside the legend border
labelspacing the vertical space between the legend entries
handlelength the length of the legend handles
handletextpad the pad between the legend handle and text
borderaxespad the pad between the axes and legend border
columnspacing the spacing between columns
title the legend title
bbox_to_anchor the bbox that the legend will be anchored.
bbox_transform the transform for the bbox. transAxes if None.
================ ==================================================================
The dimensions of pad and spacing are given as a fraction of the
_fontsize. Values from rcParams will be used if None.
Users can specify any arbitrary location for the legend using the
*bbox_to_anchor* keyword argument. bbox_to_anchor can be an instance
of BboxBase(or its derivatives) or a tuple of 2 or 4 floats.
See :meth:`set_bbox_to_anchor` for more detail.
The legend location can be specified by setting *loc* with a tuple of
2 floats, which is interpreted as the lower-left corner of the legend
in the normalized axes coordinate.
"""
from matplotlib.axes import Axes # local import only to avoid circularity
from matplotlib.figure import Figure # local import only to avoid circularity
Artist.__init__(self)
if prop is None:
self.prop=FontProperties(size=rcParams["legend.fontsize"])
elif isinstance(prop, dict):
self.prop=FontProperties(**prop)
if "size" not in prop:
self.prop.set_size(rcParams["legend.fontsize"])
else:
self.prop=prop
self._fontsize = self.prop.get_size_in_points()
propnames=['numpoints', 'markerscale', 'shadow', "columnspacing",
"scatterpoints"]
localdict = locals()
for name in propnames:
if localdict[name] is None:
value = rcParams["legend."+name]
else:
value = localdict[name]
setattr(self, name, value)
# Take care the deprecated keywords
deprecated_kwds = {"pad":"borderpad",
"labelsep":"labelspacing",
"handlelen":"handlelength",
"handletextsep":"handletextpad",
"axespad":"borderaxespad"}
# convert values of deprecated keywords (ginve in axes coords)
# to new vaules in a fraction of the font size
# conversion factor
bbox = parent.bbox
axessize_fontsize = min(bbox.width, bbox.height)/self._fontsize
for k, v in deprecated_kwds.items():
# use deprecated value if not None and if their newer
# counter part is None.
if localdict[k] is not None and localdict[v] is None:
warnings.warn("Use '%s' instead of '%s'." % (v, k),
DeprecationWarning)
setattr(self, v, localdict[k]*axessize_fontsize)
continue
# Otherwise, use new keywords
if localdict[v] is None:
setattr(self, v, rcParams["legend."+v])
else:
setattr(self, v, localdict[v])
del localdict
handles = list(handles)
if len(handles)<2:
ncol = 1
self._ncol = ncol
if self.numpoints <= 0:
raise ValueError("numpoints must be >= 0; it was %d"% numpoints)
# introduce y-offset for handles of the scatter plot
if scatteryoffsets is None:
self._scatteryoffsets = np.array([3./8., 4./8., 2.5/8.])
else:
self._scatteryoffsets = np.asarray(scatteryoffsets)
reps = int(self.numpoints / len(self._scatteryoffsets)) + 1
self._scatteryoffsets = np.tile(self._scatteryoffsets, reps)[:self.scatterpoints]
# _legend_box is an OffsetBox instance that contains all
# legend items and will be initialized from _init_legend_box()
# method.
self._legend_box = None
if isinstance(parent,Axes):
self.isaxes = True
self.set_figure(parent.figure)
elif isinstance(parent,Figure):
self.isaxes = False
self.set_figure(parent)
else:
raise TypeError("Legend needs either Axes or Figure as parent")
self.parent = parent
if loc is None:
loc = rcParams["legend.loc"]
if not self.isaxes and loc in [0,'best']:
loc = 'upper right'
if is_string_like(loc):
if loc not in self.codes:
if self.isaxes:
warnings.warn('Unrecognized location "%s". Falling back on "best"; '
'valid locations are\n\t%s\n'
% (loc, '\n\t'.join(self.codes.keys())))
loc = 0
else:
warnings.warn('Unrecognized location "%s". Falling back on "upper right"; '
'valid locations are\n\t%s\n'
% (loc, '\n\t'.join(self.codes.keys())))
loc = 1
else:
loc = self.codes[loc]
if not self.isaxes and loc == 0:
warnings.warn('Automatic legend placement (loc="best") not implemented for figure legend. '
'Falling back on "upper right".')
loc = 1
self._loc = loc
self._mode = mode
self.set_bbox_to_anchor(bbox_to_anchor, bbox_transform)
# We use FancyBboxPatch to draw a legend frame. The location
# and size of the box will be updated during the drawing time.
self.legendPatch = FancyBboxPatch(
xy=(0.0, 0.0), width=1., height=1.,
facecolor='w', edgecolor='k',
mutation_scale=self._fontsize,
snap=True
)
# The width and height of the legendPatch will be set (in the
# draw()) to the length that includes the padding. Thus we set
# pad=0 here.
if fancybox is None:
fancybox = rcParams["legend.fancybox"]
if fancybox == True:
self.legendPatch.set_boxstyle("round",pad=0,
rounding_size=0.2)
else:
self.legendPatch.set_boxstyle("square",pad=0)
self._set_artist_props(self.legendPatch)
self._drawFrame = True
# init with null renderer
self._init_legend_box(handles, labels)
self.set_title(title)
self._last_fontsize_points = self._fontsize
def _set_artist_props(self, a):
"""
set the boilerplate props for artists added to axes
"""
a.set_figure(self.figure)
for c in self.get_children():
c.set_figure(self.figure)
a.set_transform(self.get_transform())
def _findoffset_best(self, width, height, xdescent, ydescent, renderer):
"Helper function to locate the legend at its best position"
ox, oy = self._find_best_position(width, height, renderer)
return ox+xdescent, oy+ydescent
def _findoffset_loc(self, width, height, xdescent, ydescent, renderer):
"Heper function to locate the legend using the location code"
if iterable(self._loc) and len(self._loc)==2:
# when loc is a tuple of axes(or figure) coordinates.
fx, fy = self._loc
bbox = self.get_bbox_to_anchor()
x, y = bbox.x0 + bbox.width * fx, bbox.y0 + bbox.height * fy
else:
bbox = Bbox.from_bounds(0, 0, width, height)
x, y = self._get_anchored_bbox(self._loc, bbox, self.get_bbox_to_anchor(), renderer)
return x+xdescent, y+ydescent
@allow_rasterization
def draw(self, renderer):
"Draw everything that belongs to the legend"
if not self.get_visible(): return
renderer.open_group('legend')
# find_offset function will be provided to _legend_box and
# _legend_box will draw itself at the location of the return
# value of the find_offset.
if self._loc == 0:
_findoffset = self._findoffset_best
else:
_findoffset = self._findoffset_loc
def findoffset(width, height, xdescent, ydescent):
return _findoffset(width, height, xdescent, ydescent, renderer)
self._legend_box.set_offset(findoffset)
fontsize = renderer.points_to_pixels(self._fontsize)
# if mode == fill, set the width of the legend_box to the
# width of the paret (minus pads)
if self._mode in ["expand"]:
pad = 2*(self.borderaxespad+self.borderpad)*fontsize
self._legend_box.set_width(self.get_bbox_to_anchor().width-pad)
if self._drawFrame:
# update the location and size of the legend
bbox = self._legend_box.get_window_extent(renderer)
self.legendPatch.set_bounds(bbox.x0, bbox.y0,
bbox.width, bbox.height)
self.legendPatch.set_mutation_scale(fontsize)
if self.shadow:
shadow = Shadow(self.legendPatch, 2, -2)
shadow.draw(renderer)
self.legendPatch.draw(renderer)
self._legend_box.draw(renderer)
renderer.close_group('legend')
def _approx_text_height(self, renderer=None):
"""
Return the approximate height of the text. This is used to place
the legend handle.
"""
if renderer is None:
return self._fontsize
else:
return renderer.points_to_pixels(self._fontsize)
def _init_legend_box(self, handles, labels):
"""
Initiallize the legend_box. The legend_box is an instance of
the OffsetBox, which is packed with legend handles and
texts. Once packed, their location is calculated during the
drawing time.
"""
fontsize = self._fontsize
# legend_box is a HPacker, horizontally packed with
# columns. Each column is a VPacker, vertically packed with
# legend items. Each legend item is HPacker packed with
# legend handleBox and labelBox. handleBox is an instance of
# offsetbox.DrawingArea which contains legend handle. labelBox
# is an instance of offsetbox.TextArea which contains legend
# text.
text_list = [] # the list of text instances
handle_list = [] # the list of text instances
label_prop = dict(verticalalignment='baseline',
horizontalalignment='left',
fontproperties=self.prop,
)
labelboxes = []
for l in labels:
textbox = TextArea(l, textprops=label_prop,
multilinebaseline=True, minimumdescent=True)
text_list.append(textbox._text)
labelboxes.append(textbox)
handleboxes = []
# The approximate height and descent of text. These values are
# only used for plotting the legend handle.
height = self._approx_text_height() * 0.7
descent = 0.
# each handle needs to be drawn inside a box of (x, y, w, h) =
# (0, -descent, width, height). And their corrdinates should
# be given in the display coordinates.
# The transformation of each handle will be automatically set
# to self.get_trasnform(). If the artist does not uses its
# default trasnform (eg, Collections), you need to
# manually set their transform to the self.get_transform().
for handle in handles:
if isinstance(handle, RegularPolyCollection) or \
isinstance(handle, CircleCollection):
npoints = self.scatterpoints
else:
npoints = self.numpoints
if npoints > 1:
# we put some pad here to compensate the size of the
# marker
xdata = np.linspace(0.3*fontsize,
(self.handlelength-0.3)*fontsize,
npoints)
xdata_marker = xdata
elif npoints == 1:
xdata = np.linspace(0, self.handlelength*fontsize, 2)
xdata_marker = [0.5*self.handlelength*fontsize]
if isinstance(handle, Line2D):
ydata = ((height-descent)/2.)*np.ones(xdata.shape, float)
legline = Line2D(xdata, ydata)
legline.update_from(handle)
self._set_artist_props(legline) # after update
legline.set_clip_box(None)
legline.set_clip_path(None)
legline.set_drawstyle('default')
legline.set_marker('None')
handle_list.append(legline)
legline_marker = Line2D(xdata_marker, ydata[:len(xdata_marker)])
legline_marker.update_from(handle)
self._set_artist_props(legline_marker)
legline_marker.set_clip_box(None)
legline_marker.set_clip_path(None)
legline_marker.set_linestyle('None')
# we don't want to add this to the return list because
# the texts and handles are assumed to be in one-to-one
# correpondence.
legline._legmarker = legline_marker
elif isinstance(handle, Patch):
p = Rectangle(xy=(0., 0.),
width = self.handlelength*fontsize,
height=(height-descent),
)
p.update_from(handle)
self._set_artist_props(p)
p.set_clip_box(None)
p.set_clip_path(None)
handle_list.append(p)
elif isinstance(handle, LineCollection):
ydata = ((height-descent)/2.)*np.ones(xdata.shape, float)
legline = Line2D(xdata, ydata)
self._set_artist_props(legline)
legline.set_clip_box(None)
legline.set_clip_path(None)
lw = handle.get_linewidth()[0]
dashes = handle.get_dashes()[0]
color = handle.get_colors()[0]
legline.set_color(color)
legline.set_linewidth(lw)
if dashes[0] is not None: # dashed line
legline.set_dashes(dashes[1])
handle_list.append(legline)
elif isinstance(handle, RegularPolyCollection):
#ydata = self._scatteryoffsets
ydata = height*self._scatteryoffsets
size_max, size_min = max(handle.get_sizes()),\
min(handle.get_sizes())
# we may need to scale these sizes by "markerscale"
# attribute. But other handle types does not seem
# to care about this attribute and it is currently ignored.
if self.scatterpoints < 4:
sizes = [.5*(size_max+size_min), size_max,
size_min]
else:
sizes = (size_max-size_min)*np.linspace(0,1,self.scatterpoints)+size_min
p = type(handle)(handle.get_numsides(),
rotation=handle.get_rotation(),
sizes=sizes,
offsets=zip(xdata_marker,ydata),
transOffset=self.get_transform(),
)
p.update_from(handle)
p.set_figure(self.figure)
p.set_clip_box(None)
p.set_clip_path(None)
handle_list.append(p)
elif isinstance(handle, CircleCollection):
ydata = height*self._scatteryoffsets
size_max, size_min = max(handle.get_sizes()),\
min(handle.get_sizes())
# we may need to scale these sizes by "markerscale"
# attribute. But other handle types does not seem
# to care about this attribute and it is currently ignored.
if self.scatterpoints < 4:
sizes = [.5*(size_max+size_min), size_max,
size_min]
else:
sizes = (size_max-size_min)*np.linspace(0,1,self.scatterpoints)+size_min
p = type(handle)(sizes,
offsets=zip(xdata_marker,ydata),
transOffset=self.get_transform(),
)
p.update_from(handle)
p.set_figure(self.figure)
p.set_clip_box(None)
p.set_clip_path(None)
handle_list.append(p)
else:
handle_list.append(None)
handlebox = DrawingArea(width=self.handlelength*fontsize,
height=height,
xdescent=0., ydescent=descent)
handle = handle_list[-1]
handlebox.add_artist(handle)
if hasattr(handle, "_legmarker"):
handlebox.add_artist(handle._legmarker)
handleboxes.append(handlebox)
# We calculate number of lows in each column. The first
# (num_largecol) columns will have (nrows+1) rows, and remaing
# (num_smallcol) columns will have (nrows) rows.
ncol = min(self._ncol, len(handleboxes))
nrows, num_largecol = divmod(len(handleboxes), ncol)
num_smallcol = ncol-num_largecol
# starting index of each column and number of rows in it.
largecol = safezip(range(0, num_largecol*(nrows+1), (nrows+1)),
[nrows+1] * num_largecol)
smallcol = safezip(range(num_largecol*(nrows+1), len(handleboxes), nrows),
[nrows] * num_smallcol)
handle_label = safezip(handleboxes, labelboxes)
columnbox = []
for i0, di in largecol+smallcol:
# pack handleBox and labelBox into itemBox
itemBoxes = [HPacker(pad=0,
sep=self.handletextpad*fontsize,
children=[h, t], align="baseline")
for h, t in handle_label[i0:i0+di]]
# minimumdescent=False for the text of the last row of the column
itemBoxes[-1].get_children()[1].set_minimumdescent(False)
# pack columnBox
columnbox.append(VPacker(pad=0,
sep=self.labelspacing*fontsize,
align="baseline",
children=itemBoxes))
if self._mode == "expand":
mode = "expand"
else:
mode = "fixed"
sep = self.columnspacing*fontsize
self._legend_handle_box = HPacker(pad=0,
sep=sep, align="baseline",
mode=mode,
children=columnbox)
self._legend_title_box = TextArea("")
self._legend_box = VPacker(pad=self.borderpad*fontsize,
sep=self.labelspacing*fontsize,
align="center",
children=[self._legend_title_box,
self._legend_handle_box])
self._legend_box.set_figure(self.figure)
self.texts = text_list
self.legendHandles = handle_list
def _auto_legend_data(self):
"""
Returns list of vertices and extents covered by the plot.
Returns a two long list.
First element is a list of (x, y) vertices (in
display-coordinates) covered by all the lines and line
collections, in the legend's handles.
Second element is a list of bounding boxes for all the patches in
the legend's handles.
"""
assert self.isaxes # should always hold because function is only called internally
ax = self.parent
vertices = []
bboxes = []
lines = []
for handle in ax.lines:
assert isinstance(handle, Line2D)
path = handle.get_path()
trans = handle.get_transform()
tpath = trans.transform_path(path)
lines.append(tpath)
for handle in ax.patches:
assert isinstance(handle, Patch)
if isinstance(handle, Rectangle):
transform = handle.get_data_transform()
bboxes.append(handle.get_bbox().transformed(transform))
else:
transform = handle.get_transform()
bboxes.append(handle.get_path().get_extents(transform))
return [vertices, bboxes, lines]
def draw_frame(self, b):
'b is a boolean. Set draw frame to b'
self._drawFrame = b
def get_children(self):
'return a list of child artists'
children = []
if self._legend_box:
children.append(self._legend_box)
return children
def get_frame(self):
'return the Rectangle instance used to frame the legend'
return self.legendPatch
def get_lines(self):
'return a list of lines.Line2D instances in the legend'
return [h for h in self.legendHandles if isinstance(h, Line2D)]
def get_patches(self):
'return a list of patch instances in the legend'
return silent_list('Patch', [h for h in self.legendHandles if isinstance(h, Patch)])
def get_texts(self):
'return a list of text.Text instance in the legend'
return silent_list('Text', self.texts)
def set_title(self, title):
'set the legend title'
self._legend_title_box._text.set_text(title)
if title:
self._legend_title_box.set_visible(True)
else:
self._legend_title_box.set_visible(False)
def get_title(self):
'return Text instance for the legend title'
return self._legend_title_box._text
def get_window_extent(self):
'return a extent of the the legend'
return self.legendPatch.get_window_extent()
def get_bbox_to_anchor(self):
"""
return the bbox that the legend will be anchored
"""
if self._bbox_to_anchor is None:
return self.parent.bbox
else:
return self._bbox_to_anchor
def set_bbox_to_anchor(self, bbox, transform=None):
"""
set the bbox that the legend will be anchored.
*bbox* can be a BboxBase instance, a tuple of [left, bottom,
width, height] in the given transform (normalized axes
coordinate if None), or a tuple of [left, bottom] where the
width and height will be assumed to be zero.
"""
if bbox is None:
self._bbox_to_anchor = None
return
elif isinstance(bbox, BboxBase):
self._bbox_to_anchor = bbox
else:
try:
l = len(bbox)
except TypeError:
raise ValueError("Invalid argument for bbox : %s" % str(bbox))
if l == 2:
bbox = [bbox[0], bbox[1], 0, 0]
self._bbox_to_anchor = Bbox.from_bounds(*bbox)
if transform is None:
transform = BboxTransformTo(self.parent.bbox)
self._bbox_to_anchor = TransformedBbox(self._bbox_to_anchor,
transform)
def _get_anchored_bbox(self, loc, bbox, parentbbox, renderer):
"""
Place the *bbox* inside the *parentbbox* according to a given
location code. Return the (x,y) coordinate of the bbox.
- loc: a location code in range(1, 11).
This corresponds to the possible values for self._loc, excluding "best".
- bbox: bbox to be placed, display coodinate units.
- parentbbox: a parent box which will contain the bbox. In
display coordinates.
"""
assert loc in range(1,11) # called only internally
BEST, UR, UL, LL, LR, R, CL, CR, LC, UC, C = range(11)
anchor_coefs={UR:"NE",
UL:"NW",
LL:"SW",
LR:"SE",
R:"E",
CL:"W",
CR:"E",
LC:"S",
UC:"N",
C:"C"}
c = anchor_coefs[loc]
fontsize = renderer.points_to_pixels(self._fontsize)
container = parentbbox.padded(-(self.borderaxespad) * fontsize)
anchored_box = bbox.anchored(c, container=container)
return anchored_box.x0, anchored_box.y0
def _find_best_position(self, width, height, renderer, consider=None):
"""
Determine the best location to place the legend.
`consider` is a list of (x, y) pairs to consider as a potential
lower-left corner of the legend. All are display coords.
"""
assert self.isaxes # should always hold because function is only called internally
verts, bboxes, lines = self._auto_legend_data()
bbox = Bbox.from_bounds(0, 0, width, height)
consider = [self._get_anchored_bbox(x, bbox, self.get_bbox_to_anchor(),
renderer) for x in range(1, len(self.codes))]
#tx, ty = self.legendPatch.get_x(), self.legendPatch.get_y()
candidates = []
for l, b in consider:
legendBox = Bbox.from_bounds(l, b, width, height)
badness = 0
badness = legendBox.count_contains(verts)
badness += legendBox.count_overlaps(bboxes)
for line in lines:
if line.intersects_bbox(legendBox):
badness += 1
ox, oy = l, b
if badness == 0:
return ox, oy
candidates.append((badness, (l, b)))
# rather than use min() or list.sort(), do this so that we are assured
# that in the case of two equal badnesses, the one first considered is
# returned.
# NOTE: list.sort() is stable.But leave as it is for now. -JJL
minCandidate = candidates[0]
for candidate in candidates:
if candidate[0] < minCandidate[0]:
minCandidate = candidate
ox, oy = minCandidate[1]
return ox, oy