I'm trying to count given data points inside each ring of ellipse:

The problem is that I have a function to check that: so for each ellipse, to make sure whether a point is in it, three inputs have to be calculated:

```
def get_focal_point(r1,r2,center_x):
# f = square root of r1-squared - r2-squared
focal_dist = sqrt((r1**2) - (r2**2))
f1_x = center_x - focal_dist
f2_x = center_x + focal_dist
return f1_x, f2_x
def get_distance(f1,f2,center_y,t_x,t_y):
d1 = sqrt(((f1-t_x)**2) + ((center_y - t_y)**2))
d2 = sqrt(((f2-t_x)**2) + ((center_y - t_y)**2))
return d1,d2
def in_ellipse(major_ax,d1,d2):
if (d1+d2) <= 2*major_ax:
return True
else:
return False
```

Right now I'm checking whether or not it's in an ellipse by:

```
for i in range(len(data.latitude)):
t_x = data.latitude[i]
t_y = data.longitude[i]
d1,d2 = get_distance(f1,f2,center_y,t_x,t_y)
d1_array.append(d1)
d2_array.append(d2)
if in_ellipse(major_ax,d1,d2) == True:
core_count += 1
# if the point is not in core ellipse
# check the next ring up
else:
for i in range(loop):
.....
```

But I would then have to calculate each pairs of focal points of the outside loops.. is there any more efficient and or clever way to do this?