The LaTeX processor included in MATLAB is primarily designed for creating mathematical expressions, meaning that some functionality related to fonts or document processing is not supported.
As of R2020b you cannot specify a font when using LaTeX in MATLAB. However, some commands provide a similar degree of customization. In this case, a font similar to Helvetica is achieved by using '\textsf{}', which makes the font sans-serif. An example of '\textsf{}' being implemented is shown below:
str = ['$\frac{\Delta\textsf{var1}}{\Delta\textsf{var2}}$'];
xlabel(str,'Interpreter','latex','fontsize',12);
Note that '\textsf{}' needs to be applied separately to 'var1' and 'var2' as the '\Delta' character is not compatible. This implementation may also generate the following warning when executed:
Warning: Error updating Text.
Font cmss10 is not supported.
This occurs when using the LaTeX interpreter for sans-serif fonts but should not be of any concern.
