How to combine cellfun and strfind?
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bluesaturn[at]kellnerweg.de
I have 1x7 cell array with the contents:
'.' '..' 'H66000.526' 'H66001.526' 'H66002.526' 'H66003.526' 'H66004.526'
How can I combine cellfun and strfind to find '001.' in the other strings, please?
Thank you.
Walter Roberson
cellfun(@(IDX) ~isempty(IDX), strfind(TheCell, '.001'))
This will return a logical vector, one per row, true indicating that the
row matched. Is that what you were seeking, or were you looking for
the indices?
Positions = zeros(length(TheCell),1);
T = strfind(TheCell, '.001);
E = cellfun(@isempty, T);
Positions(~E) = cellfun(@(IDX) IDX(1), T(~E));
This will create Positions as 0 for rows that do not contain the string
and as the index of the first occurance of 001. for the rows that do.
us
one of the many solutions
c={'.','..','ab001','ab002','ac001'};
ix=~cellfun(@isempty,regexp(c,'001'))
% ix = 0 0 1 0 1
us
bluesaturn[at]kellnerweg.de
Yes, I was looking if there is a file containing 001. in the name. So my function gave me back the position and I could collect the name.
With the help of this group I am using now
file_position1=find(~cellfun('isempty', strfind(files_in_folder_names,'000.')));
and by knowing the position I will get the full name later.
Thank you as well for your suggestions.
Emil
str = '001';
c={'.','..','ab001','ab002','ac001'};
I find very elegant. Unfortunately does it only work on char arrays. Can this be modified such that it works for cell arrays of strings as well?
The output then would be a cell array with the same amount of elements as XX. So the statement I am looking for should behave like
str = {'001','b0'};
c={'.','..','ab001','ab002','ac001'};
ix=~cellfun(@isempty,regexp(c,str))
ix{1} = [0 0 1 0 0];
ix{2} = [0 0 1 1 0];
Any ideas?
us
one of the (more contrived) solutions
str={'001','b0'};
c={'.','..','ab001','ab002','ac001'};
ix=arrayfun(@(x) ~cellfun(@isempty,regexp(c,str(x))),1:numel(str),'uni',false);
ix=cat(1,ix{:})
%{
% ix =
0 0 1 0 1
0 0 1 1 0
%}
us
Emil
tic
for i = 1:n
for j = 1:numel(id)
ix{j} = ~cellfun(@isempty,regexp(c,str{j}));
end
end
toc
to be 2.5 times faster. I went on to check other examples and found arrayfun to always be slower than the for-loop it is replacing. When is it, performance-wise, an advantage to use arrayfun?
Oleg Komarov
Never.
Only cellfun has 3 syntaxes (the last 3 ones listed in the help) which may be at least as fast as a loop.
Oleg
Matt Fig
> Thanks, with the help your post in the other thread I came up with the same solution. It looks really elegant! However, when I compared the performance to that of a for-loop I found
>
> tic
> for i = 1:n
> for j = 1:numel(id)
> ix{j} = ~cellfun(@isempty,regexp(c,str{j}));
> end
> end
> toc
>
For even more speed use 'isempty' instead of @isempty.
Emil
Matt Fig
> Thanks for your inputs. My code works somewhat faster now. So can I conclude that the take-home message here is that for-loops actually are the way to go at times in terms of performance?
... as has been shown many(!) times on this newsgroup.
Bruno Luong
>When is it, performance-wise, an advantage to use arrayfun?
With few exception, arrayfun is cellfun are deceit features introduced by Mathworks few years ago. They are essentially disguised for-loop. Similar topic has been discussed in the pass:
http://www.mathworks.com/matlabcentral/newsreader/view_thread/253815
Bruno