matlab - Struggling to index into a column vector produced using the eval function -

i have several tables, each massive amount of data (20mb each). let's call them table_1, table_2, table_3, etc. structure of these tables similar, identical column headers (but varying number of rows). let's attribute_a, attribute_b, etc.

i interested in performing calculations on attribute_b each table. these calculations involve looping through attribute_b.

i start creating master list of table names.

table_list = [table_1, table_2, ... table 10]; 

now can iterate through , perform calculations. doing single calculations works fine using eval , concatentation of column vector name function of value of current_table:

for current_table = table_list     peak_value = max(eval(strcat(current_table,"attribute_c"))); 

i run trouble when perform calculations require iterating through column vectors. instance, following fails.

for current_table = table_list     = 1:length(eval(strcat(current_table,".attribute_b")         x = x + eval(strcat(current_table,".attribute_b"))(i); 

matlab gets hung when try marry evaluated column , desired index value of i. there way this?

i understand if made single structure of of data easier (not using string list combining data). want iterate through each of tables without re-writing data.

as excaza pointed out, usage of eval in kind of problem discouraged. 1 safer , more elegant approach use structures.

here example of program should useful uses structures

clear % intialize structure hold tables tables = struct;  % list of table names table_names = {'table_1' 'table_2' 'table_3'};  % number of tables ntables = length(table_names);  % fill tables data % tables can nested structures more 1 data item in them in % each substructure itb=1:ntables     % tables.(table_names{itb}) = rand(3);     % load files names table_n.txt     tables.(table_names{itb}) = load([table_names{itb},'.txt']); end  % perform operations on components jtb=1:ntables    % using temporary array    %     temp = [];     %     temp = tables.(table_names{jtb});    %     a(jtb) = max(max(temp));    %     b(jtb) = temp(2,1);    % .. , such    % or directly           a(jtb) = max(max(tables.(table_names{jtb})));      b(jtb) = tables.(table_names{jtb})(2,1);  end  

you have list of names , use them create either nested structures or else - arrays here - inside of main structure called tables. can populate data files, in case used rand. both collecting data , operations on can done loops. in second loop have example how can manipulate data directly or indirectly using temporary arrays.

this relatively broad topic feel free ask questions , i'll add them answer.