Pad arrays

cookbook/grid_pad.py

@@ -0,0 +1,80 @@
+"""
+Gridding: Pad gridded data
+"""
+
+from fatiando import mesher, gridder
+from fatiando.gravmag import prism
+from fatiando.vis import mpl
+import numpy as np
+
+# Generate gridded data
+shape = (101, 172)
+x, y, z = gridder.regular((-5000, 5000, -5000, 5000), shape, z=-150)
+model = [mesher.Prism(-4000, -3000, -4000, -3000, 0, 2000, {'density': 1000}),
+         mesher.Prism(-1000, 1000, -1000, 1000, 0, 2000, {'density': -900}),
+         mesher.Prism(2000, 4000, 3000, 4000, 0, 2000, {'density': 1300})]
+gz = prism.gz(x, y, z, model)
+gz = gz.reshape(shape)
+
+# Pad arrays with all the padding options
+pads = []
+xy = [x, y]
+
+# Pad with zeros, or any other number
+# (note padtype can be a string or numeric, so long as it
+# can be cast as a float.)  For example, both 0 and '0' are valid, as
+# would be any other number.
+g, nps = gridder.pad_array(gz, padtype='0')
+pads.append(g.flatten())
+
+# Pad with the mean of each vector
+g, _ = gridder.pad_array(gz, padtype='mean')
+pads.append(g.flatten())
+
+# Pad with the edge of each vector
+g, _ = gridder.pad_array(gz, padtype='edge')
+pads.append(g.flatten())
+
+# Pad with a linear taper
+g, _ = gridder.pad_array(gz, padtype='lintaper')
+pads.append(g.flatten())
+
+# Pad with the even reflection
+g, _ = gridder.pad_array(gz, padtype='reflection')
+pads.append(g.flatten())
+
+# Pad with the odd reflection
+g, _ = gridder.pad_array(gz, padtype='OddReflection')
+pads.append(g.flatten())
+
+# Pad with the odd reflection and a cosine taper (default)
+g, _ = gridder.pad_array(gz, padtype='OddReflectionTaper')
+pads.append(g.flatten())
+
+# Get coordinate vectors
+N = gridder.pad_coords(xy, gz.shape, nps)
+
+shapepad = g.shape
+
+# Generate new meshgrid and plot results
+yp = N[1]
+xp = N[0]
+titles = ['Original', 'Zero', 'Mean', 'Edge', 'Linear Taper', 'Reflection',
+          'Odd Reflection', 'Odd Reflection/Taper']
+mpl.figure(figsize=(17, 9))
+mpl.suptitle('Padding algorithms for a 2D array')
+for ii, p in enumerate(pads):
+    mpl.subplot(2, 4, ii+2)
+    mpl.axis('scaled')
+    mpl.title(titles[ii+1])
+    levels = mpl.contourf(yp*0.001, xp*0.001, p, shapepad, 15)
+    cb = mpl.colorbar()
+    mpl.contour(yp*0.001, xp*0.001, p, shapepad, levels, clabel=False,
+                linewidth=0.1)
+mpl.subplot(2, 4, 1)
+mpl.axis('scaled')
+mpl.title(titles[0])
+levels = mpl.contourf(y*0.001, x*0.001, gz, shape, 15)
+cb = mpl.colorbar()
+mpl.contour(y*0.001, x*0.001, gz, shape, levels, clabel=False, linewidth=0.1)
+mpl.show()

doc/changelog.rst

@@ -10,6 +10,12 @@ Version 0.5
 
 **Changes**:
 
+* Added several functions for padding arrays of arbitrary dimension.
+  ``fatiando.gridder.pad_array`` pads an array with a variety of padding and
+  taper options.  ``fatiando.gridder.unpad_array`` returns the original,
+  unpadded array.  ``fatiando.gridder.pad_coords`` pads the coordinate vectors
+  associated with the arrays padded above. Added Kass in the contributors.
+  (`PR 239 <https://github.com/fatiando/fatiando/pull/239>`__)
 * Better navigation for long pages in the docs by adding a sidebar with links
   to subsections.
   (`PR 275 <https://github.com/fatiando/fatiando/pull/275>`__)

doc/contributors.rst

@@ -13,6 +13,7 @@ A (hopefully) updated list of people who contributed to Fatiando a Terra:
 * Graham Markall - Continuum Analytics, Inc.
 * `Martin Bentley`_ - Nelson Mandela Metropolitan University, South Africa and AEON, South Africa
 * `Victor Almeida`_ - UERJ, Brazil.
+* `M. Andy Kass`_ - United States Geological Survey, USA
 
 .. _Leonardo Uieda: http://www.leouieda.com
 .. _Vanderlei Coelho de Oliveira Junior: http://fatiando.org/people/oliveira-jr
@@ -21,3 +22,4 @@ A (hopefully) updated list of people who contributed to Fatiando a Terra:
 .. _André Ferreira: http://fatiando.org/people/ferreira
 .. _Martin Bentley: https://twitter.com/astonsplat
 .. _Victor Almeida: http://www.pinga-lab.org/people/victor-almeida.html
+.. _M. Andy Kass: https://twitter.com/drandykass