Create an array from another and find the indices.

Hi everyone,

I have an array with variables like S,SV, V etc now I want to create a new array only with the V variable so for example;

V

SV

S

V

will become

V

V

after this I need to know the indices where I found each one of the V variables, so in this example I should get Indices = 1 and 4

Thank you for the help.

[Walter Roberson]

Are those strings, or are they numeric values? If they are numeric values, are they scalars or vectors or arrays? If they are vectors or arrays are all of them the same size?

[João]

Thx for answering. This is an array of strings I already tried to use an if cycle like this;

%most_common_string
 for i=1:744;

   if most_common_string{i} == 'V'

       periodo=most_common_string{i};

   end 
  end

but instead of getting a new array I'm getting only a cell.

Answer 1

[Jos (10584)]

MySet = {'S' 'V' 'SV' 'S' 'V' 'V' 'S' 'SV' 'V'}
MyStr = 'V'

tf = strcmp(MySet, MyStr)
index = find(tf)
KeepSet1 = MySet(tf)
KeepSet2 = repmat(MyStr,1,numel(index)) % same result

[João]

Thank you Jos, KeepSet1 is giving me all the V's but KeepSet2 is giving me an array only with VVVVVVVVVV(...) so for that I used

ind = cellfun(@(s) strcmp(s,'V'), most_common_string)

find(ind)

[Jos (10584)]

Oh, I made a small mistake. I just wanted to point out that what you want to keep are only the V's. There are numel(index) elements to keep. These elements can be retrieved from MySet using the Index OR by repeating the element a number of times. The correct code, however, is:

KeepSet2 = repmat({MyStr},1,numel(index)) % between { }

Answer 2

[Walter Roberson]

find( ismember('V', most_common_string))

[João]

Thanks for answering Walter, but when I use find I only get one index, the first index.

Maybe I was not clear, I will need to use those indices later so maybe the best is to get an array with each one of the indices values.

Answer 3

[David Sanchez]

most_common_string = {'V','SV','S','V','S'};
wanted_string='V';
idx = getnameidx(most_common_string,wanted_string);

idx = find(most_common_string==wanted_string);

k=1;
 for i=1:numel(most_common_string)

     if most_common_string{i} == 'V'
         periodo(k)=i;
         k = k+1;
     end 
   end
    periodo =

       1     4

new_string_array = most_common_string(periodo);
new_string_array = 

      'V'    'V'

[João]

Thanks for your help but I'm getting this error

??? Undefined function or method 'eq' for input arguments of type 'cell'.

Error in ==> Untitled at 110
idx = find(M==wanted_string);

if true
  % code
end