Dear all thank you for viewing my question. I found out the solution. I just had to write my new data with array2table command with variable name. Just for reference that's what i did.
data= readtable('my_file.csv');
%select only the data of interest
x1data= [data{:,3}(:,1), data{:,4}(:,1), data{:,6}(:,1), data{:,9}(:,1)];
% new data table
mydata=array2table(x1data, 'VariableNames',{'time_in_seconds','point_duration','epoch_size','stage'});