Help converting cell to matrix of doubles (Large matrix)

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nori lam
nori lam 2016-10-18
回答： nori lam 2016-10-19
Good day Matlabbers!
I have a textfile with almost a million rows that I need to format.
What I want to do is break up a string date into a double matrix that has 3 columns of [yyyy mm dd]. I dont want to make a datevec as I need the months and day.
What I have done is able to extract the date into a new matrix but does anyone have a good suggestion on how to vectorize my code so I dont have to run a loop?
Here is my code
data = {'1991-08-09' '12:15:00' 66.0 200 '(Unchecked)' 18966.0 200 '(Unchecked).calc';...
'1991-08-09' '12:30:00' 66.0 200 '(Unchecked)' 18966.0 200 '(Unchecked).calc';...
'1991-08-09' '12:45:00' 66.0 200 '(Unchecked)' 18966.0 200 '(Unchecked).calc'};
% single row
date_short = [str2num(data{1}(1:4)),str2num(data{1}(6:7)),str2num(data{1}(9:10))];
% loop to get all date rows
date_short_loop = [];
for a = 1:3
date_short_loop(a,1:3) = [str2num(data{a}(1:4)),str2num(data{a}(6:7)),str2num(data{a}(9:10))];
end
Any suggestions are greatly appreciated :) Thanks Norris

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采纳的回答

Matthew Eicholtz
Matthew Eicholtz 2016-10-18
I think datevec is what you want.
d = datevec(data(:,1),'yyyy-mm-dd');
d = d(:,1:3); % if you only want to keep the year, month, and day

更多回答（1 个）

nori lam
nori lam 2016-10-19
Thanks for the suggestion.
I tried the datevec and it is really slow (comparable to a for loop) which is unfortunate.
I ended up using the find and replace function in Sublime text to remove the '-' marks and just read the whole file with textread.

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