If you know the name of the mat file, you don't have to pass it in. As long as it is accessible (in the current folder, or in a folder that has been added to the MATLAB path), it can load it.
userInput=input("Please choose between the following numbers: 1,2 or 3.");
function Tester(userInput)
bridges=load(bridges.mat);
end
Otherwise, you can look into how to pass inputs to a function. You declare the inputs using varibles, then call the function with the actual values. For example
userInput=input("Please choose between the following numbers: 1,2 or 3.");
% call function and pass in fileName as character array
Tester('bridges.mat')
% function declaration containg variable names
function Tester(fileName,userInput)
% Inside a function, you use the variable names used in the declaration
bridges=load(fileName);
end
