how to rename columns with names like Var2_1, Var2_2...?

Writing data to an xlsx file I get this:

Var1 Var2_1 Var2_2 Var2_3

01-May-2024 2213 98 111

How can I rename Var2_n ?

renamevars and output_data.Properties.VariableNames doesn't work..

Here is my code (thanks a lot for each hint!):

% Read data from 'data.xlsx'
data = readtable('data.xlsx');

% Get unique dates
unique_dates = unique(data{:, 1}); % Assuming the date column is the first column in the table

% Initialize output table
output_data = table();

% Loop through each unique date
for i = 1:length(unique_dates)
date_data = data(strcmp(data{:, 1}, unique_dates{i}), :);

% Calculate sum of numbers for each date
sum_numbers = floor(sum(date_data{:, 3:5}, 1));

% Create a new row with Date and sum_numbers
new_row = {unique_dates{i}, sum_numbers};

% Append the new row to the output table
output_data = [output_data; new_row];
end

% Write output data to 'data-new.xlsx'

writetable(output_data, 'data-new.xlsx');

[Yash]

Hi Harald,

I am unable to understand the issue that you are facing while using "renamevars". I tried it, and it works as expected.

Kindly refer to the example below:

tbl = table([1;11;111;1111],[2;22;222;2222],[3;33;333;3333],[4;44;444;4444],'VariableNames',["Var1" "Var2_2" "Var2_3" "Var2_4"])

tbl = 4x4 table
    Var1    Var2_2    Var2_3    Var2_4
    ____    ______    ______    ______

       1        2         3         4 
      11       22        33        44 
     111      222       333       444 
    1111     2222      3333      4444 

tbl = renamevars(tbl,["Var2_2" "Var2_3" "Var2_4"],["Var2" "Var3" "Var4"])

tbl = 4x4 table
    Var1    Var2    Var3    Var4
    ____    ____    ____    ____

       1       2       3       4
      11      22      33      44
     111     222     333     444
    1111    2222    3333    4444

To better assist you, kindly let us know the issue that you are encountering.

[Harald von der Osten]

this is the error I get:

rror using tabular/renamevars (line 46)

Unrecognized table variable name 'Var1'.

Error in Counts (line 21)

output_data = renamevars(output_data,["Var1" "Var2_1" "Var2_2" "Var2_3"],["Date" "counts 1" "counts 2" "counts 3"])

Answer 1

[Star Strider]

Probably the easiest way:

data.Properties.VariableNames(2:end) = {'Var2','Var3','Var4'};

Example —

data = array2table(rand(2,4), 'VariableNames',{'Var1','Var2_1','Var2_2','Var2_3'})

data = 2x4 table
     Var1      Var2_1     Var2_2     Var2_3 
    _______    _______    _______    _______

    0.63401    0.43607    0.32244    0.37832
    0.17206    0.16586    0.91634    0.60248

data.Properties.VariableNames(2:end) = {'Var2','Var3','Var4'}

data = 2x4 table
     Var1       Var2       Var3       Var4  
    _______    _______    _______    _______

    0.63401    0.43607    0.32244    0.37832
    0.17206    0.16586    0.91634    0.60248

You can also use that approach to rename all of them, if you want to.

.

EDIT — Corrected typogrpahical errors, added information.

Answer 2

[Harald von der Osten]

solved it. I had to rewrite the code, because for Matlab the triple 'Var2_1', 'Var2_2' and 'Var2_3' was just one column...

Thanks a lot to all for your help !