Coverage for tcvx21/analysis/contour_finding_m.py: 100%

1""" 

2Implementation of a contour finding routine for 2D data 

3""" 

4import numpy as np 

5from skimage import measure 

6 

7 

8def find_contours(x_vals, y_vals, array, level: float) -> list: 

9 """ 

10 Uses skimage.measure.find_contours to find the contours of an array at a given level 

11 

12 skimage uses pixel units, so we need to convert back to real units 

13 """ 

14 x_vals, y_vals, array = np.asarray( 

15 x_vals), np.asarray(y_vals), np.asarray(array) 

16 

17 assert x_vals.size == array.shape[-1] 

18 assert y_vals.size == array.shape[-2] 

19 

20 x_spacing, y_spacing = np.mean(np.diff(x_vals)), np.mean(np.diff(y_vals)) 

21 assert np.allclose(np.diff(x_vals), x_spacing) and np.allclose( 

22 np.diff(y_vals), y_spacing), "Error: basis vectors are not equally spaced." 

23 

24 contours = measure.find_contours(array, level) 

25 # Contours is a list of numpy arrays, where the numpy arrays have the 

26 # shape (n, 2) 

27 

28 for i, contour in enumerate(contours): 

29 # For each contour level found, switch the x and y elements, and then 

30 # convert to grid units 

31 

32 x_contour, y_contour = contour[:, 1], contour[:, 0] 

33 x_contour, y_contour = x_contour * x_spacing + \ 

34 x_vals.min(), y_contour * y_spacing + y_vals.min() 

35 contours[i] = np.column_stack((x_contour, y_contour)) 

36 

37 return contours