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author | Anton Khirnov <anton@khirnov.net> | 2019-12-02 10:57:08 +0100 |
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committer | Anton Khirnov <anton@khirnov.net> | 2019-12-02 10:57:08 +0100 |
commit | 05012c2e34857f224290a69afe41b3b0cd170cde (patch) | |
tree | 6833feff6595493ab8d3a1ec9f91736311b23669 /interp.py | |
parent | 4e003ae1d42ee42dbd78b769887e2c6fda342549 (diff) |
Add an interpolation module.
Diffstat (limited to 'interp.py')
-rw-r--r-- | interp.py | 52 |
1 files changed, 52 insertions, 0 deletions
diff --git a/interp.py b/interp.py new file mode 100644 index 0000000..c57f417 --- /dev/null +++ b/interp.py @@ -0,0 +1,52 @@ +import numpy as np + +def interp1d(src_start, src_step, src_val, dst_coords, stencil): + idx_src = (dst_coords / src_step - src_start - (stencil / 2 - 1)).astype(np.int) + src_coord = np.linspace(src_start, src_start + src_step * (src_val.shape[0] - 1), + src_val.shape[0], dtype = src_val.dtype) + + fact = np.zeros((stencil, ) + idx_src.shape, dtype = src_val.dtype) + 1.0 + for i in range(stencil): + for j in range(stencil): + if i == j: + continue + + fact[i] *= (dst_coords - src_coord[idx_src + j]) / (src_coord[idx_src + i] - src_coord[idx_src + j]) + + ret = np.zeros_like(dst_coords, dtype = src_val.dtype) + for i in range(stencil): + ret += fact[i] * src_val[idx_src + i] + + return ret + +def interp2d(src_start, src_step, src_val, dst_coords, stencil): + ret = np.zeros_like(dst_coords[0], dtype = src_val.dtype) + + idx_src = [] + fact = [] + for dim in range(len(src_start)): + src_coord = np.linspace(src_start[dim], src_start[dim] + src_step[dim] * (src_val.shape[dim] - 1), + src_val.shape[dim], dtype = src_val.dtype) + + idx = ((dst_coords[dim] - src_start[dim]) / src_step[dim] - (stencil / 2 - 1)).astype(np.int) + f = np.zeros((stencil, ) + idx.shape, dtype = src_val.dtype) + 1.0 + + + for i in range(stencil): + for j in range(stencil): + if i == j: + continue + + f[i] *= (dst_coords[dim] - src_coord[idx + j]) / (src_coord[idx + i] - src_coord[idx + j]) + + idx_src.append(idx) + fact.append(f) + + for i in range(stencil): + val = np.zeros_like(ret) + for j in range(stencil): + val += fact[1][j] * src_val[idx_src[0] + i, idx_src[1] + j] + + ret += fact[0][i] * val + + return ret |