You can add the option 'orientation','horizontal' to your input for boxchart or boxplot. See examples below.
load carsmall
figure
boxplot(MPG,Origin,'orientation','horizontal')
title('Miles per Gallon by Vehicle Origin')
ylabel('Country of Origin')
xlabel('Miles per Gallon (MPG)')
figure
boxplot(MPG,Origin)
title('Miles per Gallon by Vehicle Origin')
xlabel('Country of Origin')
ylabel('Miles per Gallon (MPG)')
tsunamis = readtable('tsunamis.xlsx');
idx = contains(tsunamis.Cause,'Earthquake');
earthquakes = tsunamis(idx,:);
boxchart(earthquakes.Month,earthquakes.EarthquakeMagnitude)
xlabel('Month')
ylabel('Earthquake Magnitude')
figure
boxchart(earthquakes.Month,earthquakes.EarthquakeMagnitude,'orientation','horizontal')
ylabel('Month')
xlabel('Earthquake Magnitude')
With the data you provided:
X=[6.00
8.00
23.00
26.00
27.00
30.00];
Y=[9.00
8.00
24.00
39.00
36.00
43.00];
boxplot(X,Y,'orientation','horizontal');
figure
boxplot(X,Y,'orientation','vertical');