MATLAB: Index daily values in TT over many years to determine mean

meanparse datatimetable

I would like to determine the daily means over many years from an existing TT (attached).
Specifically, all July 01's are combined and a mean determined, all July 02's are combined and a mean detemined, etc.
I've started to do this using a brute force step-wise method and realize its going to take forever. Below is what I've done so far (and it works).
I'm just wondering if (and I think there should be) there's a much easire way to parse the data.
% Create indexes for July days.
idx_Jul1 = ismember(day(TT4_staLCA_AT_Jul.Time), 1);
idx_Jul2 = ismember(day(TT4_staLCA_AT_Jul.Time), 2);
idx_Jul3 = ismember(day(TT4_staLCA_AT_Jul.Time), 3);
idx_Jul4 = ismember(day(TT4_staLCA_AT_Jul.Time), 4);
idx_Jul5 = ismember(day(TT4_staLCA_AT_Jul.Time), 5);
idx_Jul6 = ismember(day(TT4_staLCA_AT_Jul.Time), 6);
idx_Jul7 = ismember(day(TT4_staLCA_AT_Jul.Time), 7);
idx_Jul8 = ismember(day(TT4_staLCA_AT_Jul.Time), 8);
idx_Jul9 = ismember(day(TT4_staLCA_AT_Jul.Time), 9);
idx_Jul10 = ismember(day(TT4_staLCA_AT_Jul.Time), 10);
idx_Jul11 = ismember(day(TT4_staLCA_AT_Jul.Time), 11);
idx_Jul12 = ismember(day(TT4_staLCA_AT_Jul.Time), 12);
idx_Jul13 = ismember(day(TT4_staLCA_AT_Jul.Time), 13);
idx_Jul14 = ismember(day(TT4_staLCA_AT_Jul.Time), 14);
idx_Jul15 = ismember(day(TT4_staLCA_AT_Jul.Time), 15);
idx_Jul16 = ismember(day(TT4_staLCA_AT_Jul.Time), 16);
idx_Jul17 = ismember(day(TT4_staLCA_AT_Jul.Time), 17);
idx_Jul18 = ismember(day(TT4_staLCA_AT_Jul.Time), 18);
idx_Jul19 = ismember(day(TT4_staLCA_AT_Jul.Time), 19);
idx_Jul20 = ismember(day(TT4_staLCA_AT_Jul.Time), 20);
idx_Jul21 = ismember(day(TT4_staLCA_AT_Jul.Time), 21);
idx_Jul22 = ismember(day(TT4_staLCA_AT_Jul.Time), 22);
idx_Jul23 = ismember(day(TT4_staLCA_AT_Jul.Time), 23);
idx_Jul24 = ismember(day(TT4_staLCA_AT_Jul.Time), 24);
idx_Jul25 = ismember(day(TT4_staLCA_AT_Jul.Time), 25);
idx_Jul26 = ismember(day(TT4_staLCA_AT_Jul.Time), 26);
idx_Jul27 = ismember(day(TT4_staLCA_AT_Jul.Time), 27);
idx_Jul28 = ismember(day(TT4_staLCA_AT_Jul.Time), 28);
idx_Jul29 = ismember(day(TT4_staLCA_AT_Jul.Time), 29);
idx_Jul30 = ismember(day(TT4_staLCA_AT_Jul.Time), 30);
idx_Jul31 = ismember(day(TT4_staLCA_AT_Jul.Time), 31);
% Daily indexes Jul.
TT4_staLCA_AT_Jul1 = TT4_staLCA_AT_Jul(idx_Jul1,:);
TT4_staLCA_AT_Jul1_mean = nanmean(TT4_staLCA_AT_Jul1.Var1);
TT4_staLCA_AT_Jul2 = TT4_staLCA_AT_Jul(idx_Jul2,:);
TT4_staLCA_AT_Jul2_mean = nanmean(TT4_staLCA_AT_Jul2.Var1);
TT4_staLCA_AT_Jul3 = TT4_staLCA_AT_Jul(idx_Jul3,:);
TT4_staLCA_AT_Jul3_mean = nanmean(TT4_staLCA_AT_Jul3.Var1);
TT4_staLCA_AT_Jul4 = TT4_staLCA_AT_Jul(idx_Jul4,:);
TT4_staLCA_AT_Jul4_mean = nanmean(TT4_staLCA_AT_Jul4.Var1);
TT4_staLCA_AT_Jul5 = TT4_staLCA_AT_Jul(idx_Jul5,:);
TT4_staLCA_AT_Jul5_mean = nanmean(TT4_staLCA_AT_Jul5.Var1);
TT4_staLCA_AT_Jul6 = TT4_staLCA_AT_Jul(idx_Jul6,:);
TT4_staLCA_AT_Jul6_mean = nanmean(TT4_staLCA_AT_Jul6.Var1);
TT4_staLCA_AT_Jul7 = TT4_staLCA_AT_Jul(idx_Jul7,:);
TT4_staLCA_AT_Jul7_mean = nanmean(TT4_staLCA_AT_Jul7.Var1);
TT4_staLCA_AT_Jul8 = TT4_staLCA_AT_Jul(idx_Jul8,:);
TT4_staLCA_AT_Jul8_mean = nanmean(TT4_staLCA_AT_Jul8.Var1);
TT4_staLCA_AT_Jul9 = TT4_staLCA_AT_Jul(idx_Jul9,:);
TT4_staLCA_AT_Jul9_mean = nanmean(TT4_staLCA_AT_Jul9.Var1);
TT4_staLCA_AT_Jul10 = TT4_staLCA_AT_Jul(idx_Jul10,:);
TT4_staLCA_AT_Jul10_mean = nanmean(TT4_staLCA_AT_Jul10.Var1);
TT4_staLCA_AT_Jul11 = TT4_staLCA_AT_Jul(idx_Jul11,:);
TT4_staLCA_AT_Jul11_mean = nanmean(TT4_staLCA_AT_Jul11.Var1);
TT4_staLCA_AT_Jul12 = TT4_staLCA_AT_Jul(idx_Jul12,:);
TT4_staLCA_AT_Jul12_mean = nanmean(TT4_staLCA_AT_Jul12.Var1);
TT4_staLCA_AT_Jul13 = TT4_staLCA_AT_Jul(idx_Jul13,:);
TT4_staLCA_AT_Jul13_mean = nanmean(TT4_staLCA_AT_Jul13.Var1);
TT4_staLCA_AT_Jul14 = TT4_staLCA_AT_Jul(idx_Jul14,:);
TT4_staLCA_AT_Jul14_mean = nanmean(TT4_staLCA_AT_Jul14.Var1);
TT4_staLCA_AT_Jul15 = TT4_staLCA_AT_Jul(idx_Jul15,:);
TT4_staLCA_AT_Jul15_mean = nanmean(TT4_staLCA_AT_Jul15.Var1);
TT4_staLCA_AT_Jul16 = TT4_staLCA_AT_Jul(idx_Jul16,:);
TT4_staLCA_AT_Jul16_mean = nanmean(TT4_staLCA_AT_Jul16.Var1);
TT4_staLCA_AT_Jul17 = TT4_staLCA_AT_Jul(idx_Jul17,:);
TT4_staLCA_AT_Jul17_mean = nanmean(TT4_staLCA_AT_Jul17.Var1);
TT4_staLCA_AT_Jul18 = TT4_staLCA_AT_Jul(idx_Jul18,:);
TT4_staLCA_AT_Jul18_mean = nanmean(TT4_staLCA_AT_Jul18.Var1);
TT4_staLCA_AT_Jul19 = TT4_staLCA_AT_Jul(idx_Jul19,:);
TT4_staLCA_AT_Jul19_mean = nanmean(TT4_staLCA_AT_Jul19.Var1);
TT4_staLCA_AT_Jul20 = TT4_staLCA_AT_Jul(idx_Jul20,:);
TT4_staLCA_AT_Jul20_mean = nanmean(TT4_staLCA_AT_Jul20.Var1);
TT4_staLCA_AT_Jul21 = TT4_staLCA_AT_Jul(idx_Jul21,:);
TT4_staLCA_AT_Jul21_mean = nanmean(TT4_staLCA_AT_Jul21.Var1);
TT4_staLCA_AT_Jul22 = TT4_staLCA_AT_Jul(idx_Jul22,:);
TT4_staLCA_AT_Jul22_mean = nanmean(TT4_staLCA_AT_Jul22.Var1);
TT4_staLCA_AT_Jul23 = TT4_staLCA_AT_Jul(idx_Jul23,:);
TT4_staLCA_AT_Jul23_mean = nanmean(TT4_staLCA_AT_Jul23.Var1);
TT4_staLCA_AT_Jul24 = TT4_staLCA_AT_Jul(idx_Jul24,:);
TT4_staLCA_AT_Jul24_mean = nanmean(TT4_staLCA_AT_Jul24.Var1);
TT4_staLCA_AT_Jul25 = TT4_staLCA_AT_Jul(idx_Jul25,:);
TT4_staLCA_AT_Jul25_mean = nanmean(TT4_staLCA_AT_Jul25.Var1);
TT4_staLCA_AT_Jul26 = TT4_staLCA_AT_Jul(idx_Jul26,:);
TT4_staLCA_AT_Jul26_mean = nanmean(TT4_staLCA_AT_Jul26.Var1);
TT4_staLCA_AT_Jul27 = TT4_staLCA_AT_Jul(idx_Jul27,:);
TT4_staLCA_AT_Jul27_mean = nanmean(TT4_staLCA_AT_Jul27.Var1);
TT4_staLCA_AT_Jul28 = TT4_staLCA_AT_Jul(idx_Jul28,:);
TT4_staLCA_AT_Jul28_mean = nanmean(TT4_staLCA_AT_Jul28.Var1);
TT4_staLCA_AT_Jul29 = TT4_staLCA_AT_Jul(idx_Jul29,:);
TT4_staLCA_AT_Jul29_mean = nanmean(TT4_staLCA_AT_Jul29.Var1);
TT4_staLCA_AT_Jul30 = TT4_staLCA_AT_Jul(idx_Jul30,:);
TT4_staLCA_AT_Jul30_mean = nanmean(TT4_staLCA_AT_Jul30.Var1);
TT4_staLCA_AT_Jul31 = TT4_staLCA_AT_Jul(idx_Jul31,:);
TT4_staLCA_AT_Jul31_mean = nanmean(TT4_staLCA_AT_Jul31.Var1);
% Combine all means into one matrix.
TT5_staLCA_AT_Jul = [TT4_staLCA_AT_Jul1_mean; TT4_staLCA_AT_Jul2_mean; TT4_staLCA_AT_Jul3_mean; TT4_staLCA_AT_Jul4_mean; TT4_staLCA_AT_Jul5_mean; TT4_staLCA_AT_Jul6_mean;...
TT4_staLCA_AT_Jul7_mean; TT4_staLCA_AT_Jul8_mean; TT4_staLCA_AT_Jul9_mean; TT4_staLCA_AT_Jul10_mean; TT4_staLCA_AT_Jul11_mean; TT4_staLCA_AT_Jul12_mean;...
TT4_staLCA_AT_Jul13_mean; TT4_staLCA_AT_Jul14_mean; TT4_staLCA_AT_Jul15_mean; TT4_staLCA_AT_Jul16_mean; TT4_staLCA_AT_Jul17_mean; TT4_staLCA_AT_Jul18_mean;...
TT4_staLCA_AT_Jul19_mean; TT4_staLCA_AT_Jul20_mean; TT4_staLCA_AT_Jul21_mean; TT4_staLCA_AT_Jul22_mean; TT4_staLCA_AT_Jul23_mean; TT4_staLCA_AT_Jul24_mean;...
TT4_staLCA_AT_Jul25_mean; TT4_staLCA_AT_Jul26_mean; TT4_staLCA_AT_Jul27_mean; TT4_staLCA_AT_Jul28_mean; TT4_staLCA_AT_Jul29_mean; TT4_staLCA_AT_Jul30_mean;...
TT4_staLCA_AT_Jul31_mean;];
% Create a column vector for july days used in plotting.
Jul_length = (1:31);
Jul_length = Jul_length';
% Plot July average AT
figure
scatter(Jul_length, TT5_staLCA_AT_Jul)

Best Answer

This will create a table with the average for each day of the year (1-366). 'dayofmonth' might be preferable for just July data to avoid leap year issues
summary_table = groupsummary(TT4_staLCA_AT_Jul,'Time','dayofyear','mean');