packages/vaex-core/vaex/dataframe.py
def first(self, expression, order_expression, binby=[], limits=None, shape=default_shape, selection=False, delay=False, edges=False, progress=None):
        """Return the first element of a binned `expression`, where the values each bin are sorted by `order_expression`.

        Example:

        >>> import vaex
        >>> df = vaex.example()
        >>> df.first(df.x, df.y, shape=8)
        >>> df.first(df.x, df.y, shape=8, binby=[df.y])
        >>> df.first(df.x, df.y, shape=8, binby=[df.y])
        array([-4.81883764, 11.65378   ,  9.70084476, -7.3025589 ,  4.84954977,
                8.47446537, -5.73602629, 10.18783   ])

        :param expression: The value to be placed in the bin.
        :param order_expression: Order the values in the bins by this expression.
        :param binby: {binby}
        :param limits: {limits}
        :param shape: {shape}
        :param selection: {selection}
        :param delay: {delay}
        :param progress: {progress}
        :param edges: {edges}
        :return: Ndarray containing the first elements.
        :rtype: numpy.array
        """
        return self._compute_agg('first', expression, binby, limits, shape, selection, delay, edges, progress, extra_expressions=[order_expression])
        logger.debug("count(%r, binby=%r, limits=%r)", expression, binby, limits)
        logger.debug("count(%r, binby=%r, limits=%r)", expression, binby, limits)
        expression = _ensure_strings_from_expressions(expression)
        order_expression = _ensure_string_from_expression(order_expression)
        binby = _ensure_strings_from_expressions(binby)
        waslist, [expressions,] = vaex.utils.listify(expression)
        @delayed
        def finish(*counts):
            counts = np.asarray(counts)
            return vaex.utils.unlistify(waslist, counts)
        progressbar = vaex.utils.progressbars(progress)
        limits = self.limits(binby, limits, delay=True, shape=shape)
        stats = [self._first_calculation(expression, order_expression, binby=binby, limits=limits, shape=shape, selection=selection, edges=edges, progressbar=progressbar) for expression in expressions]
        var = finish(*stats)
        return self._delay(delay, var)
def first(self, expression, order_expression, binby=[], limits=None, shape=default_shape, selection=False, delay=False, edges=False, progress=None):
        """Return the first element of a binned `expression`, where the values each bin are sorted by `order_expression`.

        Example:

        >>> import vaex
        >>> df = vaex.example()
        >>> df.first(df.x, df.y, shape=8)
        >>> df.first(df.x, df.y, shape=8, binby=[df.y])
        >>> df.first(df.x, df.y, shape=8, binby=[df.y])
        array([-4.81883764, 11.65378   ,  9.70084476, -7.3025589 ,  4.84954977,
                8.47446537, -5.73602629, 10.18783   ])

        :param expression: The value to be placed in the bin.
        :param order_expression: Order the values in the bins by this expression.
        :param binby: {binby}
        :param limits: {limits}
        :param shape: {shape}
        :param selection: {selection}
        :param delay: {delay}
        :param progress: {progress}
        :param edges: {edges}
        :return: Ndarray containing the first elements.
        :rtype: numpy.array
        """
        return self._compute_agg('first', expression, binby, limits, shape, selection, delay, edges, progress, extra_expressions=[order_expression])
        logger.debug("count(%r, binby=%r, limits=%r)", expression, binby, limits)
        logger.debug("count(%r, binby=%r, limits=%r)", expression, binby, limits)
        expression = _ensure_strings_from_expressions(expression)
        order_expression = _ensure_string_from_expression(order_expression)
        binby = _ensure_strings_from_expressions(binby)
        waslist, [expressions,] = vaex.utils.listify(expression)
        @delayed
        def finish(*counts):
            counts = np.asarray(counts)
            return vaex.utils.unlistify(waslist, counts)
        progressbar = vaex.utils.progressbars(progress)
        limits = self.limits(binby, limits, delay=True, shape=shape)
        stats = [self._first_calculation(expression, order_expression, binby=binby, limits=limits, shape=shape, selection=selection, edges=edges, progressbar=progressbar) for expression in expressions]
        var = finish(*stats)
        return self._delay(delay, var)
Return the first element of a binned `expression`, where the values each bin are sorted by `order_expression`.

        Example:

        >>> import vaex
        >>> df = vaex.example()
        >>> df.first(df.x, df.y, shape=8)
        >>> df.first(df.x, df.y, shape=8, binby=[df.y])
        >>> df.first(df.x, df.y, shape=8, binby=[df.y])
        array([-4.81883764, 11.65378   ,  9.70084476, -7.3025589 ,  4.84954977,
                8.47446537, -5.73602629, 10.18783   ])

        :param expression: The value to be placed in the bin.
        :param order_expression: Order the values in the bins by this expression.
        :param binby: {binby}
        :param limits: {limits}
        :param shape: {shape}
        :param selection: {selection}
        :param delay: {delay}
        :param progress: {progress}
        :param edges: {edges}
        :return: Ndarray containing the first elements.
        :rtype: numpy.array