Incorporating Structure Fields into a Function as Inputs

I'm using MATLAB (Mapping Toolbox) to create a large number of lines between different countries. Since there are so many lines, I'm trying to do this using object-oriented programming. This is the method I've written:

function transline = createlines(transline,Name,base.CapTr.val(a,b),base.EtrOut.val(:,a,b,1),base.EtrOut.val(:,b,a,1),base.EtrIn.val(:,a,b,1),base.EtrIn.val(:,b,a,1),... coords(c,2),coords(c,1),coords(d,2),coords(d,1))

where base is a struct and I intend to substitute different values for 'a' and 'b', e.g., base.CapTr.val(3,4) and create new objects.

The problem is I can't include base.CapTr.val(a,b) and the subsequent entries as inputs to the function because MATLAB declares the '.' to be an unexpected operator.

So, can you please tell me how I can add varying values of base.CapTr.val(a,b), etc. as inputs to the function?

I don't know if I've explained my problem properly, but I hope it's clear.

Thank you.

Answer 1

[Cedric]

I am not sure that I understand what you are trying to do .. so you have a class e.g. Transline, which contains a method createlines

 methods
    function transline = Transline( .. some input args .. )
       transline = .. some initialization ..
    end
    function transline = createlines(transline, .. additional input args .. )
       .. body of the method ..
    end
 end

Now when createlines is called as e.g.

 transline = transline.createlines(S, 8, [3,4]) ;

the object is "stored into" (or accessible through) the transline that is a local variable and an input argument to the function createlines, S is stored into the second argument, etc, such as if creatlines were declared as

 function transline = createlines(transline, arg2, arg3, arg4)

you would have S from the call available through arg2, 8 from the call available through arg3 and [3,4] from the call available through arg4.

Then you could do whatever you want with arg2.f1 and arg2.f2 within the method. In particular, if these two fields contain arrays, you could index them using values of properties, or extra args passed during the call. You could also pass directly relevant values at the call. What you cannot do is to write the function declaration using indexed structures (arrays, structs, etc) in place of "flat" argument names.

More explicitly, if the class defines properties

 properties
   coord, countryID, lines
 end

with coord a struct with fields lon and lat, you can do either

 function transline = createlines(transline, lon, lat)
    transline.lines = ... something based on lon and lat ...
 end

with a call like

 id = transline.countryID ;
 coord = transline.coord ;
 transline = transline.createlines(coord.lon(id), coord.lat(id)) ;

or

 function transline = createlines(transline, coord, countryID)
    transline.lines = ... something based on coord.lon(countryID) and 
                           coord.lat(countryID) ...
 end

with a call like

 transline = transline.createlines(transline.coord, transline.countryID) ;

but not

 function transline = ...
    createlines(transline, transline.coord.lat(transline.countryID), ..etc)
    ...
 end

because "transline.coord.lat(transline.countryID)" doesn't provide MATLAB with a valid name for a local variable (which is what input arguments are ultimately).

Hope it helps (at least to refine your question if needed)!

[Usman]

Thank you for your help. I guess I now know what I was doing wrong. I'll try to rectify my mistake and hope that I'm more successful this time :)

[Cedric]

You're welcome! Let me know if anything is still unclear, and please [ Accept ] my answer if I fully solved your problem.

Cheers!

Cedric

[Usman]

OK. Will do. I'm trying it out right now. :)

[Usman]

Hi Cedric,

Thanks a lot for your help!!!

Best regards,

Usman