Input A of class cell and input B of class cell must be cell arrays of strings, unless one is a string".

tickers='tickers.txt'; %list of tickers of financial stocks
price=hist_stock_data('09032015','09032016',tickers); %download data from yahoo.finanace
prices=zeros(size(price(1, 1).AdjClose,1),size(price,2));
for t=1:size(price,2);
    prices(:,t)= price(1, t).AdjClose;
end
%I create an array in which I have a list of tickers called nomes 
for t=1:size(price,2);
nomes{1,t}=price(1, t).Ticker;
end
%couple is a string array nx2 with all possible pairs obtained from the “nomes”
cl=num2cell(prices); %to obtain a cell
ff=[nomes;cl]; %to have a matrix in which the first row is the name of stocks, and over there the historical prices for each stocks
%Now I want to obtain a for loop in which for each pair extrapolate the historical price from the matrix “prices”, utilizing the function ismember.
    for ii=1:size(couple,1);
        looking_up=couple(ii,:);
    [tf, coldix]=ismember(looking_up,ff(ii,:));
    Prices=ff(:,coldix(tf));
    prices=prices(2:end,:);
    prices=cell2mat(prices);
    x(ii)=prices(:,2);
    y(ii)=prices(:,1);
    end

but give me the following error: Input A of class cell and input B of class cell must be cell arrays of strings, unless one is a string".

[Walter Roberson]

Why did you ask the same question three times? Now someone has to go in and try to merge the three different versions :(

Answer 1

[Stephen23]

The message seems quite clear: you are providing a cell array to ismember, but it is not cell arrays of strings. The function ismember accepts certain combinations of input variable classes, as its documentation explains:

" B must belong to the same class as A with the following exceptions:"

• "logical, char, and all numeric classes can combine with double arrays."
• "Cell arrays of strings can combine with char arrays."
• ...

Read your code:

• looking_up is defined with looking_up=couple(ii,:), and your notes say is "couple is a string array nx2". So looking_up is a char array.
• ff is defined as ff=[nomes;cl]. It is not clear what class nomes has, but cl is defined from as cl=num2cell(prices), where prices=zeros(...), so cl is clearly a cell array of numerics (and not a cell array of strings!)

So you are trying to call ismember on:

• looking_up, a char array.
• ff, a mixed cell array containing something (char?) and numerics.

There is no case listed in the documentation that supports this combination. As the documentation states, ismember works on two cell arrays of strings, or a char array and a cell array of strings, or on two numeric arrays, or a numeric array and a char array, but not on this mixture that you are attempting.

[fede]

ok thanks. How can i solve this situatuib?

[Stephen23]

Ask the person who wrote the code what they expected by calling ismember on a cell of strings and cell of numerics. Ask them to correct their algorithm so that they actually compare things that can be compared (e.g. cell of strings with another cell of strings, or any of the other combinations listed in the documentation).

[fede]

ismember and its loop for are created to extrapolate for each pair (for example stock1 and stock2) their historical price from the matrix "price" to obtain:

stock1 stock2
55.6  556.5
55.8  556.8
...   ...

[Stephen23]

There are likely efficient ways of doing this, but I have no idea what form your data are in. If you can provide some small examples of the input data and also an explain how you want the output to be like, then I can help with the code.

[fede]

I have the following matrix:

Name_1 Name_2 ..... Name_n
23.5    25.8          29.6
24.5    85.5 ........ 59.2

A matrix (nxn), where in the first row ther'is the name of stocks, and in the other row the historical price. Then, I have another matrix of pair of stocks, for example:

Name_1  Name_2
Name_3 Name_5

and so on.... I want a code that give me for all pair the respective stock prince. For example for the first pair: Name_1 Name_2 I want to extrapolate the following matrix:

Name_1 Name_2
23.5   25.8
24.5   85.2

and so on. Thxs

[fede]

any news? :)

[Stephen23]

inpC = {'Name_1','Name_2','Name_3','Name_4','Name_5';...
            23.5,    25.8,    29.6,    24.6,    29.6;...
            24.5,    85.5,    59.2,    75.1,    1000};
%
pairs = {'Name_1','Name_2';...
         'Name_3','Name_5';...
         'Name_2','Name_4'};
%
[~,Z] = ismember(pairs',inpC(1,:));
out = reshape(inpC(:,Z),3,2,[])

and this is the output:

out(:,:,1) = 
    'Name_1'    'Name_2'
    [  23.5]    [  25.8]
    [  24.5]    [  85.5]
out(:,:,2) = 
    'Name_3'    'Name_5'
    [  29.6]    [  29.6]
    [  59.2]    [  1000]
out(:,:,3) = 
    'Name_2'    'Name_4'
    [  25.8]    [  24.6]
    [  85.5]    [  75.1]

As is usually the case with MATLAB, the task can be solved much simpler without any loops.