storing tables in an array and calling them whithin a for loop

Question

farshid balaneji 2017-9-1

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/354876-storing-tables-in-an-array-and-calling-them-whithin-a-for-loop

回答： Peter Perkins 2017-9-1

I am a novice in MatLab. I have 30 different tables that imported in Matlab as CSV files. I want to choose two pairs of the tables and read a column Return of them and store it in ret_1 and ret_2 variables. Something like the following code:

data = {'AAPL', 'AXP', 'BBN'};
for i = length(data)
    for j = length(data)
         ret_1 = data(i).Return;
         ret_2 = data(j).Return;
    end
end

But I get an error, as data(i) doesn't include the content that I want to. I tried

eval(data(i)) but it says that eval() works only with strings and not arrays.

My data looks like the following in CSV files that I imported them into MatLab.

'AAPL' = 
     Date      Low       Close        Return
6/3/1997    16.750    16.935        16.687      
6/4/1997    16.625    16.756        16.625      
6/5/1997    16.625    17.125        16.687      
'AXP' =
   Date       Low         Close       Return
6/3/1997    69.079     70.075       68.750  
6/4/1997    69.079     69.079       68.500  
6/5/1997    68.078     69.876       67.750

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Answer 1

Peter Perkins 2017-9-1

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/354876-storing-tables-in-an-array-and-calling-them-whithin-a-for-loop#answer_280016

在 MATLAB Online 中打开

You've shown your data, but that can't possibly be output from MATLAB because

'AAPL' =

is not something MATLAB would ever display. I'm gonna assume you've done something like

aapl = readtable('aapl.csv');
axp = readtable('axp.csv');
...

It's almost never a good idea to try to do this via an eval. A reasonable thing to do might be to use a scalar struct with fields named 'aapl', etc. So

data.aapl = readtable('aapl.csv');
data.axp = readtable('axp.csv');

and then

fn = fieldnames(data);
for i = 1:length(fn)
    for j = 1:length(fn)
        ret_1 = data.(fn{i}).Return;
        ret_2 = data.(fn{j}).Return;
    end
end