use eval to define a variable from table and a name stored as cell

The cell data{} has 9 tables and i created another cell which is called c_data which contains variable names from the tables (data9 ,.... data1). In each tabel 160 variables are storred, and i need to fetch anoly those which are in c_data.

data = {dataD9 dataD8 dataD7 dataD6 dataD5 dataD4 dataD3 dataD2 dataD1};

c_data = {'IspFuel_Corr'; 'IspCOEo_Corr'; 'IspNOEo_Corr'; 'IspNOXEo_Corr'; 'IspTHCEo_Corr'; 'ArbInd1'; 'EffEngComb'; 'AI50_1'; 'MfIna'; 'LamdBrettEo'; 'PExhVes_1'; 'PExhVes_2'; 'PAirVes_1'; 'PAirVes_1'; 'Ssa_Esa'};

i use eval to create a variable z = data{:,i}.eval(c_data{k,1});

- with data{:,i} i loop all 9 tables which are in the data cell

- with eval(c_data{k,1}) i want to add the name to the variable to data{:,1}

in other words what i woudl like to have is : z = data{:,1}.IspFuel_Corr; ... first loop

z = data{:,1}.IspCOEo_Corr; ... second loop

.....

z= data{:,1}.Ssa_Esa; ... 15th loop or last loop for k, and then the same it should be done with data{:,2}. =>>> z = data{:,2}.IspFuel_Corr;

z = data{:,2}.IspCOEo_Corr; and so on until loop i is done.

the code and the error below:

data = {dataD9 dataD8 dataD7 dataD6 dataD5 dataD4 dataD3 dataD2 dataD1};

c_data = {'IspFuel_Corr'; 'IspCOEo_Corr'; 'IspNOEo_Corr'; 'IspNOXEo_Corr'; 'IspTHCEo_Corr'; 'ArbInd1'; 'EffEngComb'; 'AI50_1'; 'MfIna'; 'LamdBrettEo'; 'PExhVes_1'; 'PExhVes_2'; 'PAirVes_1'; 'PAirVes_1'; 'Ssa_Esa'};

for k = 1: length (c_data)

for i= 1:length(data)

% nexttile(t)

% savename = ['IspFuel_Corr'];

y = data{:,i}.Svt_ActAng_A; %iVVT

x = data{:,i}.Sve_ActAng_A; %eVVT

z= data{:,i}.eval(c_data{k,1});

end

end

Error using tabular/dotParenReference (line 69)

Unrecognized table variable name 'eval'.

Error in VVT_plots (line 38)

z= data{:,i}.eval(c_data{k,1});

Answer 1

[Stephen23]

EVAL is anti-pattern red-herring. Avoid EVAL.

The actual solution is to use the methods shown in the MATLAB documentation:

https://www.mathworks.com/help/matlab/matlab_prog/access-data-in-a-table.html

For example you can easily use the table.(expression) notation:

for ii = 1:numel(data)
    for jj = 1:numel(c_data)
        tbl = data{ii}; % clearer with a temporary variable
        y = tbl.Svt_ActAng_A;
        x = tbl.Sve_ActAng_A;
        z = tbl.(c_data{jj});
    end %      ^^          ^  just like the documentation shows
end

This is simpler and much more efficient than what you were attempting using evil EVAL. And it works.

[Steven Lord]

An approach I find even simpler is to just use the variable name as an index.

T = array2table(magic(4))

T = 4×4 table
    Var1    Var2    Var3    Var4
    ____    ____    ____    ____

     16       2       3      13 
      5      11      10       8 
      9       7       6      12 
      4      14      15       1 

s = 'Var3';
asATableArray = T(:, s)

asATableArray = 4×1 table
    Var3
    ____

      3 
     10 
      6 
     15 

asANumericArray = T{:, s}

asANumericArray = 4×1

3 10 6 15

Answer 2

[ST]

Thanks Stephen53,

this line was the breaktrough:

tbl = data{ii}; % clearer with a temporary variable

As simple as it is :)