There are a number of unanswered questions re Arrows here.
I just ran into yet another problem that could be alleviated with specifying start and endpoints
for the annotation.
import holoviews as hv; hv.extension('bokeh',logo=False)
hv.Curve([y*y for y in np.linspace(0,1,100)])*hv.Arrow( 60, 0.36, 'here','<')
shows the problem. Actually, I ran into this, with the label outside the frame
Here is a hack to add arrows and labels to a plot:
G = nx.Graph()
G.add_edges_from([[0,1],[0,2],[0,3]])
nx.set_node_attributes(G, {0: {"text": ""}, 1: {"text": "a"}, 2: {"text": "b"}, 3: {"text": "c"}} )
pos = { 0: np.array([0,0]), 1: np.array([1,0]), 2: np.array([0,1]), 3: np.array([0.5,0.2]) }
graph = hv.Graph.from_networkx(G, pos).opts(directed=True, node_alpha=0, arrowhead_length=0.05)
labels = hv.Labels( graph.nodes, ['x', 'y'], "text")
x = np.linspace(-1,1,20)
hv.Curve( (x,x*x)).opts(padding=0.1) * graph * labels.opts(xoffset=0.08, yoffset=0.01)
Packaged this…
class ArrowsWithLabels:
def __init__(self):
self.reset()
def reset(self):
self.G = nx.Graph()
self.E = {}
self.pos = {}
self.text = {}
self.color = {}
def _add( self, point_id, point_pos, lbl_id, lbl_pos, text, at_start=False, color='black' ):
self.E[(point_id,lbl_id)] = text
self.color[(point_id,lbl_id)] = color
self.pos[point_id] = np.array(point_pos)
self.pos[lbl_id] = np.array(lbl_pos)
self.text[point_id if at_start else lbl_id] = {"text" : text, "color": color}
def _add_lbl( self, lbl_id, point_id, delta, text, color="black" ):
#print( f"adding {delta} for {lbl_id} to current {point_id} at {self.pos[point_id]}")
self.G.add_node(lbl_id)
self.pos[lbl_id] = self.pos[point_id] + delta
self.text[lbl_id] = {"text" : text, "color": color}
def add( self, point_pos, lbl_pos, text, at_start=False, offset=None, color='black'):
cur = len( self.pos )+1
if offset is None:
self._add( cur, point_pos, cur+1, lbl_pos, text, at_start, color )
else:
self._add( cur, point_pos, cur+1, lbl_pos, "", at_start, color )
diff = self.pos[cur+1] - self.pos[cur]
diff_pos = offset * diff / np.linalg.norm( diff)
if at_start:
self._add_lbl( cur+2, cur, -diff_pos, text, color)
else:
self._add_lbl( cur+2, cur+1, diff_pos, text, color)
def graph(self):
_ = [self.text.__setitem__(k,{"text": "", "color": "black"}) for k in self.pos.keys() if self.text.get(k,None) is None]
#self.G.add_edges_from(self.E.keys())
for e in self.E.keys():
self.G.add_edge( *e, color=self.color[e])
nx.set_node_attributes( self.G, self.text )
graph = hv.Graph.from_networkx(self.G, self.pos).opts(directed=True, node_alpha=0, arrowhead_length=0.05)
lbls = hv.Labels( graph.nodes, ['x', 'y'], ["text","color"]).opts(text_color='color')
return graph,lbls
def _dbg(self):
print("Pos")
for i in self.pos.keys():
print( f". {i, self.pos[i]}")
print("Edge")
for i in self.E.keys():
print( f". {i, self.E[i]}")
print("Text")
for i in self.text.keys():
print( f". {i, self.text[i]}")
pl = ArrowsWithLabels()
pl.add( (0,0), (1,0), "X", offset=0.1, color='green')
pl.add( (0,0), (0,1), "Y", offset=0.05, color='green')
pl.add( (0,0), (1,1), "q_1", offset=0.1)
pl.add( (0.8,0.5*0.5), (0.5,0.5*0.5), "??", at_start=True, offset=0.1, color="red")
arrows,lbls = pl.graph()
#pl._dbg()
x = np.linspace(-1,1,20)
(hv.Curve( (x,x*x)) * arrows * lbls)\
.opts(hv.opts.Graph( edge_color="color"),
hv.opts.Curve( xlim = (-1,1.5), ylim = (-0.05,1.4), width=400 ))