search the second column of a cell array according to the values in the first column

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Sergio Rossi 2014-5-7

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编辑： Sergio Rossi 2014-5-7

I'm working in MATLAB and I have the following cell array:

pippo = 
'FSize'           [       10]
'MSize'           [       10]
'rho'             [      997]
'u2'              [  86.2262]
'n'               [      100]
'nimp'            [        2]
'impeller1dir'    [1x66 char]
'impeller2dir'    [1x66 char]
'comparedir'      [1x57 char]

I would like to return the content of the cell, in the second column, which corresponds to a given value for the cell in the first column of the first row. I.e., if the input is 'nimp', I want to return 2. Is there a simple way to do this which doesn't involve looping, or is looping the only way?

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Answer 1

Andrei Bobrov 2014-5-7

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out = pippo{ismember(pippo(:,1),'nimp'),2};

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Roberto 2014-5-7

great answer!!

Sergio Rossi 2014-5-7

编辑：Sergio Rossi 2014-5-7

在 MATLAB Online 中打开

Great! I was given this solution, too:

out = pippo{strcmp(pippo(:,1),'nimp'),2};

which does the same ( ismember is more generic, though, and works regardless of the types of elements in the first column of parameters ). However, my favourite is:

pippo=containers.Map(pippo(:,1),pippo(:,2))

You can then retrieve any value simply by accessing the container with the corresponding key:

out=pippo2('nimp');

Didn't know MATLAB had containers! Looks like a great solution. What do you think?

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Answer 2

Roberto 2014-5-7

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https://ww2.mathworks.cn/matlabcentral/answers/128687-search-the-second-column-of-a-cell-array-according-to-the-values-in-the-first-column#answer_135926

在 MATLAB Online 中打开

I'd recommend the use of structures:

pippo.FSize= 10;
pippo.MSize= 10;
pippo.rho= 997;
pippo.u2= 86.2262;

So when you want a member, just type:

>> pippo.FSize
    ans = 
        10

but if it cannot be done, try to use a code like this:

pippo = {'test',4;'Some',5} ;
 searched = 'some';
 returned = [];
 for i  = 1: numel(pippo)/2
     if strcmpi(pippo{i,1},searched)
         returned = pippo{i,2};
     end
 end
 disp(returned);