Question

dataset allows us to do:

x = rand(10, 1); 
y = rand(10, 1);
d = dataset(x, y);

d will have 2 variables with name ‘x’ and ‘y’ and content x and y – variable names are obtained from the workspace. The dataset() call above is equivalent to:

d = dataset({'x', x}, {'y', y});

when the names are specified.

Now if I have a subclass of dataset:

classdef mydataset < dataset
properties
end

methods
    function spec = mydataset(varargin)
        spec = spec@dataset(varargin{:});    
        % Add some more things to this subclass because that's the reason I need a subclass
    end 
end 
end    

The problem is, if I call:

d = mydataset(x);

d will have the variable x but the name is just ‘var1’. The workspace name ‘x’ is not recognized. Unless I call:

d = mydataset({'x', x});

I will not get the same effect.

Any solution?

Note that I do not want to lose other argument parsing abilities of dataset(). It can process really complicated arguments, and I do want to preserve that.

http://www.mathworks.com/help/toolbox/stats/dataset.html

A = dataset(varspec,'ParamName',Value)
A = dataset('File',filename,'ParamName',Value)
A = dataset('XLSFile',filename,'ParamName',Value)
A = dataset('XPTFile',xptfilename,'ParamName',Value)

The example in this question with mydataset(x) is the a simple and commonly encountered situation that mydataset() can’t pass things to dataset() and obtain the same results. Thus it’s an important situation. But to do just that and lose other capabilities of dataset() is not worth it.

Answer 1

One option is to capture the argument names yourself and build a cell that you then pass in to the dataset constructor, i.e. you build a cell that looks like

{{Var1 VarName1}, {Var2 VarName2}, ...}

A quick and dirty solution:

classdef mydataset < dataset

    properties
    end

    methods

        function self = mydataset(varargin)

            for k = 1:nargin
                args{k} = {varargin{k}, inputname(k)};
            end

            self = self@dataset(args{:});

        end

    end

end

Now if I call it:

>> x=1;
>> y=2;
>> mydataset(x,y)
ans = 
    x    y
    1    2

Of course, you’ve now lost the ability to call mydataset with the {val, valname},... syntax, but maybe that’s worth giving up. If you also wanted to be able to do that, you would need to write a conditional that checks the format of your input first, and builds args differently depending on the input format.

Note that you can’t do the obvious thing and put your calls to the superclass constructor inside two branches of an if statement. In Matlab, calls to the superclass have to be at the top level (i.e. you can’t put them inside loops or conditionals).