'Update the y values to be interpolated
The barycentric interpolation algorithm requires the calculation
of weights, but these depend only on the xi. The yi can be changed
at any time.
Parameters
yi : array_like
The y coordinates of the points the polynomial should pass through.
If None, the y values will be supplied later.
axis : int, optional
Axis in the yi array corresponding to the x-coordinate values.'

def set_yi(self, yi, axis=None):

    if (yi is None):
        self.yi = None
        return
    self._set_yi(yi, xi=self.xi, axis=axis)
    self.yi = self._reshape_yi(yi)
    (self.n, self.r) = self.yi.shape
