Change the x values to categorical data type -
x=[1:3,8];
y=[500 500 500 500
69 535 1354 42
97 498 1357 48
73 539 1328 60];
x=categorical(x);
bar(x,y);
Another workaround is to plot serially and then change the tick-labels
x=[1:3,8];
y=[500 500 500 500
69 535 1354 42
97 498 1357 48
73 539 1328 60];
bar(1:numel(x),y);
xticklabels(x)