How to efficiently replace value at the n last column?
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balandong
am 4 Sep. 2018
Kommentiert: balandong
am 4 Sep. 2018
Dear all, The objective was to replace the value at the end of a column. I have make a simple case but wonder if there is another way to make it more compact and efficient?
Thanks in advance
f_sbj=2
sA=23;
A =1:sA;
appndOut=cell(sA,1);
for f_x=1:sA
Out = nchoosek(A, f_x);
[rows, columns] = find(Out==f_sbj);
Out(rows, :) = [];
[m,n] = size(Out );
newNan=nan(m,(sA-n));
appndOut{f_x}=[newNan Out];
end
2 Kommentare
Walter Roberson
am 4 Sep. 2018
That code appears to insert at the beginning of columns, not replace at the end of columns.
The code can be made more compact, but not necessarily more efficient.
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Walter Roberson
am 4 Sep. 2018
lastNcol = @(M, N) M(:,end-N+1:end);
NanPrePad = @(M, N) lastNcol( [nan(size(M,1), N), M], N);
select_and_prepad = @(M, N) NanPrePad( M(all(M~=f_sbj, 2),:) );
appndOut = arrayfun(@(f_x) select_and_prepad(nchoosek(A, f_x), sA), (1:sA).', 'uniform', 0);
You can use shorter names for the anonymous functions if you find the above to not be compact enough.
Though I wonder why you do not do something like
A = setdiff(1:sA, f_sbj);
That would eliminate the possibility of f_sbj being generated by the nchoosek, so it would not be necessary to delete any rows containing f_sbj.
3 Kommentare
Walter Roberson
am 4 Sep. 2018
f_sbj=2
sA=23;
A =1:sA;
lastNcol = @(M, N) M(:,end-N+1:end);
NanPrePad = @(M, N) lastNcol( [nan(size(M,1), N), M], N);
select_and_prepad = @(M, N) NanPrePad( M(all(M~=f_sbj, 2),:), N );
appndOut = arrayfun(@(f_x) select_and_prepad(nchoosek(A, f_x), sA), (1:sA).', 'uniform', 0);
This takes a moment to execute.
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