How can I convert a equation into an character array?

Hi community,

I want to convert an equation like: N=1-X into an character array like: Z='N=1-X' or the other way around. The problem is functions like string2num() do not accept variables as input.

[Matt J]

Convert to a character array from what? In what form does the input equation exist? As a symbolic expression?

[Emre Sahin]

I am currently programming a GUI, where I am using in different functions different equations as the z-axis in surf plots. I also need to show the same equation as a label on the z-axis in the surf plot and on a static text field. Therefore I need to convert the function to an character array. To do that I want to use the previously defined equation without typing it all the way again.

[Guillaume]

Again, as Matt asked, what form does the equation takes in your code? There are many ways to code an equation for plotting and the answer is going to depend on how you've done it.

[Emre Sahin]

I don't exactly know what you mean, I will just show an example code:

 classdef Formfunctions < handle

    methods(Static)  

        function surfplot(handles,X,Y,N)
            s=surf(X,Y,N);
            s.FaceColor='interp';
            a=gca;
            a.Box='on';
            zlim([0 1]);
            xlabel('x')
            ylabel('y')
            % I want to display the function instead of N %
            zlabel('N')
            % I want to show the function N on the static text field%
            set(handles.text,'string', N)
        end

        function Node1plot(handles,X,Y)  
            %Nr.1%
            N1=1/4*(1-X).*(1-Y);

            figure('Name','Plot Formfunctions: Node1plot',...
                   'NumberTitle','off', 'Units', 'Normalized', ...
                   'OuterPosition', [0.5 0 0.5 1]);
            colormap(jet)
            Formfunctions.surfplot(handles,X,Y,N1)
        end

        function Node2plot(handles,X,Y)  
            %Nr.2%
            N2=1/4*(1+X).*(1-Y);

            figure('Name','Plot Formfunction: Node2plot',...
                   'NumberTitle','off', 'Units', 'Normalized', ...
                   'OuterPosition', [0.5 0 0.5 1]);
            colormap(jet)
            Formfunctions.surfplot(handles,X,Y,N2)
        end  
    end
end

In the main function I will just have the comands:

    if(blabla==bla)
       Formfunctions.Node1plot(handles,X,Y);

    elseif(blabla==blala)
       Formfunctions.Node2plot(handles,X,Y); 
    end

I hope that it is know clear.

Answer 1

[Matt J]

    methods(Static)  
        function surfplot(handles,X,Y,fun)  %<---change
            s=surf(X,Y,fun(X,Y));
            s.FaceColor='interp';
            a=gca;
            a.Box='on';
            zlim([0 1]);
            xlabel('x')
            ylabel('y')
            % I want to display the function instead of N %

            N=strrep( func2str(fun) ,'@(x,y)','' );  %<---change
            zlabel( N )
            % I want to show the function N on the static text field%
            set(handles.text,'string', N)
        end

        function Node1plot(handles,X,Y)  

            fun=@(x,y) 1/4*(1-x).*(1-y);  %<---change

            figure('Name','Plot Formfunctions: Node1plot',...
                   'NumberTitle','off', 'Units', 'Normalized', ...
                   'OuterPosition', [0.5 0 0.5 1]);
            colormap(jet)
            Formfunktionen.surfplot(handles,X,Y,fun)  %<---change
        end

     end