interp: add irregular 1D interpolation

1 files changed, 19 insertions, 0 deletions

diff --git a/interp.py b/interp.py
index c567758..757d927 100644
--- a/interp.py
+++ b/interp.py
@@ -21,6 +21,25 @@ def interp1d(src_start, src_step, src_val, dst_coords, stencil):
 
     return ret
 
+def interp1d_irregular(src_coord, src_val, dst_coord, stencil):
+    idx_src = np.empty(dst_coord.shape, dtype = np.int)
+    for i, dc in enumerate(dst_coord):
+        idx_src[i] = np.where(src_coord - dc < 0, src_coord, -np.inf).argmax() - stencil / 2 + 1
+
+    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_coord - src_coord[idx_src + j]) / (src_coord[idx_src + i] - src_coord[idx_src + j])
+
+    ret = np.zeros_like(dst_coord, 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)