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Control Break Processing

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luke
luke on 20 Jul 2011
[EDIT: 20110720 16:05 CDT - reformat - WDR]
I have 3 column vectors (Date1 Date2 and Error) and what I want to do is create the column named Target. Target is a 1 if it is the smallest error by Date1 and Date2 AND error is < .10 otherwise its a 0.
I can do this using for loops, BUT I was wondering if I can do this using logical indexing....I am guessing that this will be faster since I won't have to nest3 for loops.
Date1 Date2 error Target
'06-Nov-2000' '16-Dec-2000' 0.47 0
'06-Nov-2000' '16-Dec-2000' 0.41 0
'06-Nov-2000' '16-Dec-2000' 0.29 0
'06-Nov-2000' '16-Dec-2000' 0.14 0
'06-Nov-2000' '16-Dec-2000' 0.03 1
'06-Nov-2000' '16-Dec-2000' 0.18 0
'06-Nov-2000' '18-Nov-2000' 0.03 1
'06-Nov-2000' '18-Nov-2000' 0.31 0
'06-Nov-2000' '18-Nov-2000' 0.44 0
'06-Nov-2000' '18-Nov-2000' 0.45 0
'06-Nov-2000' '18-Nov-2000' 0.44 0
'06-Nov-2000' '18-Nov-2000' 0.44 0
'06-Nov-2000' '18-Nov-2000' 0.45 0
'06-Nov-2000' '18-Nov-2000' 0.45 0
'07-Nov-2000' '18-Nov-2000' 0.36 0
'07-Nov-2000' '18-Nov-2000' 0.09 1
'07-Nov-2000' '18-Nov-2000' 0.15 0
'07-Nov-2000' '18-Nov-2000' 0.38 0
'07-Nov-2000' '18-Nov-2000' 0.48 0
'07-Nov-2000' 18-Dec-2000' 0.50 0
'07-Nov-2000' 18-Dec-2000' 0.01 1
'07-Nov-2000' 18-Dec-2000' 0.15 0

Accepted Answer

Fangjun Jiang
Fangjun Jiang on 20 Jul 2011
I have one solution but it still requires a for-loop.
raw={'06-Nov-2000' '16-Dec-2000' 0.47 0
'06-Nov-2000' '16-Dec-2000' 0.41 0
'06-Nov-2000' '16-Dec-2000' 0.29 0
'06-Nov-2000' '16-Dec-2000' 0.14 0
'06-Nov-2000' '16-Dec-2000' 0.03 1
'06-Nov-2000' '16-Dec-2000' 0.18 0
'06-Nov-2000' '18-Nov-2000' 0.03 1
'06-Nov-2000' '18-Nov-2000' 0.31 0
'06-Nov-2000' '18-Nov-2000' 0.44 0
'06-Nov-2000' '18-Nov-2000' 0.45 0
'06-Nov-2000' '18-Nov-2000' 0.44 0
'06-Nov-2000' '18-Nov-2000' 0.44 0
'06-Nov-2000' '18-Nov-2000' 0.45 0
'06-Nov-2000' '18-Nov-2000' 0.45 0
'07-Nov-2000' '18-Nov-2000' 0.36 0
'07-Nov-2000' '18-Nov-2000' 0.09 1
'07-Nov-2000' '18-Nov-2000' 0.15 0
'07-Nov-2000' '18-Nov-2000' 0.38 0
'07-Nov-2000' '18-Nov-2000' 0.48 0
'07-Nov-2000' '18-Dec-2000' 0.50 0
'07-Nov-2000' '18-Dec-2000' 0.01 1
'07-Nov-2000' '18-Dec-2000' 0.15 0};
% Date1 is your first column, nx1 cell array of strings
% Date2 is your second column, nx1 cell array of strings.
% Err is your third column, nx1 double array
Date1=raw(:,1);
Date2=raw(:,2);
Err=cell2mat(raw(:,3));
RawTarget=cell2mat(raw(:,4));
Target=false(size(Err));
Date=cellstr(cell2mat([Date1,Date2]));
UniqueDate=unique(Date);
for k=1:length(UniqueDate)
Index=ismember(Date,UniqueDate(k));
Loc=find(Index);
[Dummy,MinIndex]=min(Err(Index));
Target(Loc(MinIndex))=true;
end
Target=and(Target, Err<0.1);
all(Target==RawTarget)
  5 Comments
luke
luke on 22 Jul 2011
I stand corrected. I must have changed something in the code.
Thanks! Now I need to go thru this so that I understand how it works

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More Answers (1)

Nathan Greco
Nathan Greco on 20 Jul 2011
Here's a dirty method, but no handwritten loops as requested.
Assume tmp contains your 22x3 cell array of data (the 4th column will be computed).
%storing strings as unique identifiers
tmp2 = cellfun(@(x,y)[x y],tmp(:,1),tmp(:,2),'un',0);
%get unique blocks:
[m m m] = unique(tmp2);
%get error column:
err = [tmp{:,3}];
%get target:
target = arrayfun(@(x)any(ismember(accumarray(m,err,[],@(x)min(x)),x)&x<.10),err,'un',0)';
%add target to original cell array:
tmp = [tmp target];
Hopefully this helps. It does the trick, but not sure about the speed. Anyone want to speed mine up?
Also note that loops don't necessarily mean SLOW anymore in Matlab. Try some timings on solutions provided versus your own to see what is best for you.

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