Initial commit

Author: andymilne

spTrunc.m

@@ -0,0 +1,45 @@
+function spC = spTrunc(lo,hi,spA)
+%SPTRUNC Truncate a sparse array structure.
+%   spC = spTrunc(limits,spA): Truncate a sparse array, represented as a sparse
+%   array structure or a full array, so all entries with subscripts lower than
+%   the corresponding entries in the row vector 'lo', and higher than the
+%   corresponding entries in the row vector 'hi' are removed. The output is
+%   sparse array structure with size hi-lo+1.
+%
+%   Version 1.0 by Andrew J. Milne, The MARCS Institute, Western Sydney
+%   University, 2018-01-09
+
+if nargin ~= 3
+    error('Three arguments are required.')
+end
+if size(lo,1)>1 || size(hi,1)>1
+    error('''lo'' and ''hi'' must be row vectors.')
+end
+% If full array, make into sparse array structure
+if ~isstruct(spA)
+    spA = array2spArray(spA);
+end
+if numel(lo) ~= numel(spA.Size) || numel(hi) ~= numel(spA.Size)
+    error('''lo'' and ''hi'' must have the same number of entries as dimensions in the sparse array structure.')
+end
+
+subsA = spInd2spSub(spA);
+
+dimC = hi-lo+1;
+valC = spA.Val;
+subsC = subsA;
+
+valC = valC(all(subsC>=lo & subsC<=hi,2),:);
+subsC = subsC(all(subsC>=lo & subsC<=hi,2),:);
+subsC = subsC - lo + 1;
+
+% convert subsC to linear index for array of size dimC
+if isempty(subsC)
+    warning('All array entries have been truncated.')
+    indC = [];
+    valC = [];
+else
+    indC = spSub2spInd(dimC,subsC);
+end
+% Make the sparse array structure
+spC = struct('Size',dimC,'Ind',indC,'Val',valC);