MATLAB Answers


How to simplify this and make it efficient

Asked by Martin
on 5 Sep 2019
Latest activity Edited by Martin
on 6 Sep 2019
I have a 1x500 cell (res) with a structure in each, and a 300x3 table (G). I need to check for each combination if strcmp between the field res{j}.fir and each row in G.
If it is equal I need to add the field from res 'thisisstring' to a new 4. column in the table G. The following works but is so slooow....
for i = 1:size(G{:,1},1)
for j = 1:size(res,2)
if strcmp(res{j}.fir,G{i,1}{1})
G{i,4} = res{j}.thisisstring;
If someone have an idea to simplify this it would be great!


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1 Answer

Answer by Bruno Luong
on 5 Sep 2019
Edited by Bruno Luong
on 6 Sep 2019
 Accepted Answer

NOTE: what a messy and bad data structure. There might be a much better way than working cell of structs and table.
% Generate test data
S = string(ceil(10*rand(300,3)));
G = table(S(:,1),S(:,2),S(:,3));
fir = num2cell(string(ceil(10*rand(1,500)+5)));
thisisstring = num2cell(string(ceil(100*rand(1,500)+100)));
res = num2cell(struct('fir',fir,'thisisstring',thisisstring));
clear S fir thisisstring % only G and res stay
% Engine here, do the same thing than your double for loops
[b,loc] = ismember( G{:,1}, cellfun(@(r) r.fir, res));
G(b,4) = table(cellfun(@(r) r.thisisstring, res(loc(b)))');
% Check the result


Well, with such a question I gave above, I only hope for a direction from people, - that is why I asked if someone have an "idea". Your answer was in details and that is nice, but no one forced you to make that work and answer me. I replied I had to alter a thing just in case if others search for a corresponding problem and got difficulties with your functions (like I had).
I'm not forced, but I don't like to lost my time for something that I can avoid, because I don't like to communicate back/forth with people who asks, gets a solution and discover that it doesn't exactly solve their problem because they failed to give complete details then they are stuck.
This is fortunately not your case, but most of the people who asks are like this.
This is what we (helpers) resquest is very well stated in this tutorial.
You should read especially point No. 5
"A common cause for delays in getting an acceptable solution is posting code that doesn't run because it was snipped out of the middle of a program and required variables were assigned in code above that was not included with the Answers post."
I know that is frustrating and that makes completly sense! I would never get back to you with a question like mine. That's why I spent 4-5 hours after your answer to get the string() solution. I knew if someone had a direction of an algorithm I could figure it out. After I did that, I accepted your answer, gave a like, and added a little comment that probably can help others. Thanks Bruno and especially for your answer!

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