How to align XTicks with boxplots, code and the output is attached ?

rmse1=[rmse_wavelet_anfis_his;rmse_wavelet_anfis;rmse_QDM_his;rmse_QDM;...
    rmse_QM_his;rmse_QM;rmse_raw_his;rmse_raw];
mae1=[mae_wavelet_anfis_his;mae_wavelet_anfis;mae_QDM_his;mae_QDM;...
    mae_QM_his;mae_QM;mae_raw_his;mae_raw];
g = ones(size(rmse_raw));
g = [g;g*2;g*3;g*4;g*5;g*6;g*7;g*8];
g=categorical(g);
p= tiledlayout(1,2,'TileSpacing','none');
ax1 = nexttile;
b1= boxchart(ax1,g,rmse1,'GroupByColor',g,'BoxWidth',3);
ax2=nexttile;
b2= boxchart(ax2,g,mae1,'GroupByColor',g,'BoxWidth',3);
for i=1:8
    remaind=rem(i,2);
    if remaind==1
        b1(i).SeriesIndex=1;
        b2(i).SeriesIndex=1;
    else
        b1(i).SeriesIndex=2;
        b2(i).SeriesIndex=2; 
    end
end

Answer 1

[Cris LaPierre]

See this answer: https://www.mathworks.com/matlabcentral/answers/1949893-how-to-avoid-horizontal-shifts-after-applying-groupbycolor-on-boxcharts?s_tid=srchtitle

When you group by color, boxchart expects there to be a boxplot for each group at each tick. It therefore makes space for that, centering the grouped boxplots around each tick.

If you want to set the color for each boxchart and have it aligned with an xtick, you must plot each boxplot individually, as Adam Danz shows in the linked answer.

[Avijit Paul]

Thanks a lot. Matlab can update the boxchart function, for this scenario that, whenever there is one boxchart for one xtick, it can automatically allign with the xticks.