Help with User defined function

Could someone please explain how to write the first lines of a user definded function in Matlab?

including:

function [y] = UnitConversionsFunction(x,)

what do u put after the (x,...) if i am making a function full of unit conversions.

%unit conversions
switch 
    case 'c2f'%cel to fah
        y=(x*9/5)+32;
 
    case 'f2c'%fah to cel
        y=(x-32)*5/9;
    case 'mil2fo'%milliltres to fluid ounce
        y= x/29.5735;
    case 'fo2mil'%fluid ounce to millilitres
        y= x*29.5735;
    case 'l2p'%litre to pints
        y= x*1.75975;
    case 'p2l'%pints to litres
        y= x/1.75975;
    case 'l2g'%litres to gallons
        y=x/4.54609;
  
    case 'g2l'%gallons to litres
        y= x*4.54609;
    case 'kilj2kilc' %kiloj to kiloc
        y=x/4.184;
    case 'kilc2kilj'%kiloc to kiloj
        y= 4.184*x;
    case 'pas2psi' %pas to psi
        y= x/6894.76;
     
    case 'psi2pas' %psi to pas
        y= x*6894.76;
        
end

Thanks

Answer 1

[Subhadeep Koley]

function y = UnitConversionsFunction(x, options)

% Validate that value is a character vector or string scalar. (Works only with R2020b or above)
mustBeTextScalar(options)

% Convert to lowercase
options = lower(options);

%unit conversions
switch options
    case 'c2f'%cel to fah
        y =(x*9/5)+32;
    case 'f2c'%fah to cel
        y =(x-32)*5/9;
    case 'mil2fo'%milliltres to fluid ounce
        y = x/29.5735;
    case 'fo2mil'%fluid ounce to millilitres
        y = x*29.5735;
    case 'l2p'%litre to pints
        y = x*1.75975;
    case 'p2l'%pints to litres
        y = x/1.75975;
    case 'l2g'%litres to gallons
        y=x/4.54609;  
    case 'g2l'%gallons to litres
        y = x*4.54609;
    case 'kilj2kilc' %kiloj to kiloc
        y = x/4.184;
    case 'kilc2kilj'%kiloc to kiloj
        y = 4.184*x;
    case 'pas2psi' %pas to psi
        y = x/6894.76;  
    case 'psi2pas' %psi to pas
        y = x*6894.76;  
    otherwise
        error('Please enter correct option')    
end
end

Invoke the function like,

res = UnitConversionsFunction(10, "f2C")