Label outside of the box in a figure

You can use the property Editor to change/manage the position and font size of the axes. Click Edit, then Axes Properties. In the window which appears, you can click on the upper x axis Label and drag it down, or even reduce it's font size so it stays within the window.

After all the editings are done, if you want a MATLAB code for it, click File from the menu and then Generate code.

The code I tried generating is like below,

function createfigure1
%CREATEFIGURE1

%  Auto-generated by MATLAB on 17-Apr-2018 12:32:53

% Create figure
figure1 = figure;

% Create axes
axes('Parent',figure1);

% Create xlabel
xlabel('Outer diameter, mm');

% Create axes
axes1 = axes('Parent',figure1);

% Create xlabel
xlabel('Outer diameter, in');

% Create ylabel
ylabel('Transformation Shear Strain (%)');

% Set the remaining axes properties
set(axes1,'Color','none','XAxisLocation','top');

Hope this helps!