Source code for datashader.glyphs.points

from __future__ import absolute_import, division
import numpy as np
from toolz import memoize

from datashader.glyphs.glyph import Glyph
from datashader.utils import isreal, ngjit


class _PointLike(Glyph):
    """Shared methods between Point and Line"""
    def __init__(self, x, y):
        self.x = x
        self.y = y

    @property
    def ndims(self):
        return 1

    @property
    def inputs(self):
        return (self.x, self.y)

    def validate(self, in_dshape):
        if not isreal(in_dshape.measure[str(self.x)]):
            raise ValueError('x must be real')
        elif not isreal(in_dshape.measure[str(self.y)]):
            raise ValueError('y must be real')

    @property
    def x_label(self):
        return self.x

    @property
    def y_label(self):
        return self.y

    def required_columns(self):
        return [self.x, self.y]

    def compute_x_bounds(self, df):
        bounds = self._compute_x_bounds(df[self.x].values)
        return self.maybe_expand_bounds(bounds)

    def compute_y_bounds(self, df):
        bounds = self._compute_y_bounds(df[self.y].values)
        return self.maybe_expand_bounds(bounds)

    @memoize
    def compute_bounds_dask(self, ddf):

        r = ddf.map_partitions(lambda df: np.array([[
            np.nanmin(df[self.x].values),
            np.nanmax(df[self.x].values),
            np.nanmin(df[self.y].values),
            np.nanmax(df[self.y].values)]]
        )).compute()

        x_extents = np.nanmin(r[:, 0]), np.nanmax(r[:, 1])
        y_extents = np.nanmin(r[:, 2]), np.nanmax(r[:, 3])

        return (self.maybe_expand_bounds(x_extents),
                self.maybe_expand_bounds(y_extents))


[docs]class Point(_PointLike): """A point, with center at ``x`` and ``y``. Points map each record to a single bin. Points falling exactly on the upper bounds are treated as a special case, mapping into the previous bin rather than being cropped off. Parameters ---------- x, y : str Column names for the x and y coordinates of each point. """ @memoize def _build_extend(self, x_mapper, y_mapper, info, append): x_name = self.x y_name = self.y @ngjit @self.expand_aggs_and_cols(append) def _extend(vt, bounds, xs, ys, *aggs_and_cols): sx, tx, sy, ty = vt xmin, xmax, ymin, ymax = bounds def map_onto_pixel(x, y): """Map points onto pixel grid. Points falling on upper bound are mapped into previous bin. """ xx = int(x_mapper(x) * sx + tx) yy = int(y_mapper(y) * sy + ty) return (xx - 1 if x == xmax else xx, yy - 1 if y == ymax else yy) for i in range(xs.shape[0]): x = xs[i] y = ys[i] # points outside bounds are dropped; remainder # are mapped onto pixels if (xmin <= x <= xmax) and (ymin <= y <= ymax): xi, yi = map_onto_pixel(x, y) append(i, xi, yi, *aggs_and_cols) def extend(aggs, df, vt, bounds): xs = df[x_name].values ys = df[y_name].values cols = aggs + info(df) _extend(vt, bounds, xs, ys, *cols) return extend