Factored out packer

A    packer.py

fluents/lib/packer.py

@@ -0,0 +1,28 @@
+class Packer:
+    """A compression object used to speed up model calculations.
+
+    Often used in conjunction with crossvalidation and perturbations
+    analysis. 
+    """
+    def __init__(self,array):
+        self._shape = array.shape
+        self._array = array
+        self._packed_data = None
+        
+    def expand(self,a):
+        if self._inflater!=None:
+            return dot(self._inflater,a)
+        
+    def collapse(self,axis=None,mode='svd'):
+        if not axis:
+            axis = argmin(self._array.shape) # default is the smallest dim
+
+        if axis == 1:
+            self._array = self._array.T
+        u, s, vt = svd(self._array,full_matrices=0)
+        self._inflater = vt.T
+        self._packed_data = u*s
+        return self._packed_data
+
+    def get_packed_data(self):
+        return self._packed_data