Initial commit

Author: andymilne

spFlip.m

@@ -0,0 +1,49 @@
+function spC = spFlip(spA,dim)
+%SPFLIP Flip order of entries in dimensions specified in 'dim'.
+%   spC = spFlip(spA,dim): Flip the order of entries of the full array,
+%   represented as a sparse array structure or full array, in the dimensions
+%   specified in the row vector or scalar 'dim'. The output is a sparse array
+%   structure.
+%
+%   Version 1.0 by Andrew J. Milne, The MARCS Institute, Western Sydney
+%   University, 2018-01-16
+%
+%   See also FLIP.
+
+% If full array, convert to sparse array structure
+if nargin < 2
+    error('Two arguments are required.')
+end
+if ~isstruct(spA)
+    spA = array2spArray(spA);
+end
+if any(dim<1)
+    error('All entries in ''dim'' must be positive integers.')
+end
+
+nDimA = numel(spA.Size);
+dim(dim>nDimA) = [];
+dim = unique(dim);
+if numel(dim) == nDimA
+    % simpler calculation if all dimensions are flipped
+    indA = prod(spA.Size) - spA.Ind + 1;
+else
+    logDim = zeros(1,nDimA);
+    % vector of 1s for flips and 0s for no flips
+    logDim(dim) = 1;
+    % vector of 1s for flips and -1s for no flips
+    mult = logDim;
+    mult(logDim==0) = -1;
+    % convert to subs
+    subA = spInd2spSub(spA);
+    % do the flips
+    flipSubA = (logDim.*spA.Size - subA + logDim).*mult;
+    % convert to linearindex
+    indA = spSub2spInd(spA.Size,flipSubA);
+end
+
+% Make the sparse array structure
+spC = struct('Size',spA.Size,'Ind',indA,'Val',spA.Val);
+
+end
+