[Scipy-svn] r6365 - in trunk: doc/release doc/source scipy/linalg scipy/linalg/tests

[scipy-svn at scipy.org]

Author: warren.weckesser
Date: 2010-05-01 17:26:34 -0500 (Sat, 01 May 2010)
New Revision: 6365

Modified:
   trunk/doc/release/0.8.0-notes.rst
   trunk/doc/source/linalg.rst
   trunk/scipy/linalg/info.py
   trunk/scipy/linalg/special_matrices.py
   trunk/scipy/linalg/tests/test_special_matrices.py
Log:
ENH: linalg: Added a function to create a Leslie matrix.

Modified: trunk/doc/release/0.8.0-notes.rst
===================================================================
--- trunk/doc/release/0.8.0-notes.rst	2010-04-30 16:38:37 UTC (rev 6364)
+++ trunk/doc/release/0.8.0-notes.rst	2010-05-01 22:26:34 UTC (rev 6365)
@@ -108,8 +108,8 @@
 
 New functions and other changes in scipy.linalg
 -----------------------------------------------
-The functions `circulant`, `hadamard` and `cho_solve_banded` were added
-to `scipy.linalg`.
+The functions `cho_solve_banded`, `circulant`, `hadamard` and `leslie` 
+were added to `scipy.linalg`.
 
 The function `block_diag` was enhanced to accept scalar and 1D arguments,
 along with the usual 2D arguments.

Modified: trunk/doc/source/linalg.rst
===================================================================
--- trunk/doc/source/linalg.rst	2010-04-30 16:38:37 UTC (rev 6364)
+++ trunk/doc/source/linalg.rst	2010-05-01 22:26:34 UTC (rev 6365)
@@ -87,6 +87,7 @@
    hadamard
    hankel
    kron
+   leslie
    toeplitz
    tri
    tril

Modified: trunk/scipy/linalg/info.py
===================================================================
--- trunk/scipy/linalg/info.py	2010-04-30 16:38:37 UTC (rev 6364)
+++ trunk/scipy/linalg/info.py	2010-05-01 22:26:34 UTC (rev 6365)
@@ -65,6 +65,7 @@
    hadamard   --- Hadamard matrix of order 2^n
    hankel     --- Hankel matrix
    kron       --- Kronecker product of two arrays.
+   leslie     --- Leslie matrix
    toeplitz   --- Toeplitz matrix
    tri        --- Construct a matrix filled with ones at and below a given diagonal. 
    tril       --- Construct a lower-triangular matrix from a given matrix.

Modified: trunk/scipy/linalg/special_matrices.py
===================================================================
--- trunk/scipy/linalg/special_matrices.py	2010-04-30 16:38:37 UTC (rev 6364)
+++ trunk/scipy/linalg/special_matrices.py	2010-05-01 22:26:34 UTC (rev 6365)
@@ -320,6 +320,54 @@
 
     return H
 
+
+def leslie(f, s):
+    """Create a Leslie matrix.
+    
+    Parameters
+    ----------
+    f : array-like, 1D
+        The "fecundity" coefficients.
+    s : array-like, 1D
+        The "survival" coefficients.  The length of `s` must be one less
+        than the length of `f`, and it must be at least 1.
+
+    Returns
+    -------
+    L : ndarray, 2D
+        Returns a 2D numpy ndarray with shape `(n,n)`, where `n` is the
+        length of `f`.  The array is zero except for the first row,
+        which is `f`, and the first subdiagonal, which is `s`.
+        The data type of the array will be the data type of `f[0]+s[0]`.
+
+    Examples
+    --------
+    >>> leslie([0.1, 2.0, 1.0, 0.1], [0.2, 0.8, 0.7])
+    array([[ 0.1,  2. ,  1. ,  0.1],
+           [ 0.2,  0. ,  0. ,  0. ],
+           [ 0. ,  0.8,  0. ,  0. ],
+           [ 0. ,  0. ,  0.7,  0. ]])
+    """
+    f = np.atleast_1d(f)
+    s = np.atleast_1d(s)
+    if f.ndim != 1:
+        raise ValueError("Incorrect shape for f.  f must be one-dimensional")
+    if s.ndim != 1:
+        raise ValueError("Incorrect shape for s.  s must be one-dimensional")
+    if f.size != s.size + 1:
+        raise ValueError("Incorrect lengths for f and s.  The length"
+                         " of s must be one less than the length of f.")
+    if s.size == 0:
+        raise ValueError("The length of s must be at least 1.")
+
+    tmp = f[0] + s[0]
+    n = f.size
+    a = np.zeros((n,n), dtype=tmp.dtype)
+    a[0] = f
+    a[range(1,n), range(0,n-1)] = s
+    return a
+
+
 def all_mat(*args):
     return map(np.matrix,args)
 

Modified: trunk/scipy/linalg/tests/test_special_matrices.py
===================================================================
--- trunk/scipy/linalg/tests/test_special_matrices.py	2010-04-30 16:38:37 UTC (rev 6364)
+++ trunk/scipy/linalg/tests/test_special_matrices.py	2010-05-01 22:26:34 UTC (rev 6365)
@@ -3,8 +3,8 @@
 from numpy import arange, add, array, eye, all, copy
 from numpy.testing import *
 
-from scipy.linalg import toeplitz, hankel, circulant, hadamard, tri, triu, tril, \
-                            kron, block_diag
+from scipy.linalg import toeplitz, hankel, circulant, hadamard, leslie, \
+                            tri, triu, tril, kron, block_diag
 
 
 def get_mat(n):
@@ -173,6 +173,23 @@
         assert_raises(ValueError, hadamard, 5)
 
 
+class TestLeslie(TestCase):
+
+    def test_bad_shapes(self):
+        assert_raises(ValueError, leslie, [[1,1],[2,2]], [3,4,5])        
+        assert_raises(ValueError, leslie, [3,4,5], [[1,1],[2,2]])
+        assert_raises(ValueError, leslie, [1,2], [1,2])
+        assert_raises(ValueError, leslie, [1], [])
+
+    def test_basic(self):
+        a = leslie([1, 2, 3], [0.25, 0.5])
+        expected = array([
+            [1.0,  2.0, 3.0],
+            [0.25, 0.0, 0.0],
+            [0.0,  0.5, 0.0]])
+        assert_array_equal(a, expected)
+
+
 class TestBlockDiag:
     def test_basic(self):
         x = block_diag(eye(2), [[1,2], [3,4], [5,6]], [[1, 2, 3]])