How can I plot using a string in MATLAB?

I am looking to automate some plotting for work and needing to know how I can take a variable string (string changes based upon selection in MATLAB GUI) and then use that to generate a plot.

Example..

function plotting_fcn(bool1, bool2, boo3)

    x1 = [1,2,3,4,5];
    y1 = [10,20,30,40,50];
    y2 = [20,30,40,50,60];
    y3 = [30,40,50,60,70];
    y4 = [30,40,50,60,70];

    str = 'x, [y1';

    if(bool1 == 1)
      str = strcat(str, ',y2');
    end

    if(bool2 == 1)
      str = strcat(str, ',y3');
    end

    if(bool3 == 1)
      str = strcat(str, ',y4');
    end

    str = strcat(str, '];');

    % HOWEVER I CAN CONVERT str INTO SOMETHING THAT CAN BE PLOTTED. 

    plot(x, str)

end

If there is another way to do this I am all ears (eyes), but I don't want to have to create plotting code for each of the 3! scenarios that exist for this plot.

Please Help,

Thanks,

Kellen

[Kellen Madsen]

Just realized that I added an extra x in and it should just be...

plot(str)

[Andrew Newell]

The variable x isn't defined. Do you mean x1? Also, y3 and y4 are identical. Should they be?

[Kellen Madsen]

Andrew this is just made up code, I apologize for the errors in the code, the concept I am looking to have answered is the ability to generate a string, that can be passed into a function, and then used for plotting. I should have stated the problem better.

Answer 1

[Andrew Newell]

It's not necessary to have all those conditional statements. Just use indexing:

function plotting_fcn(idx)
% Note: idx could be Boolean or it could be one or more numbers between 1
% and 4.
   x = [1,2,3,4,5];
   y = [10,20,30,40,50; ...
   20,30,40,50,60; ...
   30,40,50,60,70; ...
   30,40,50,60,70];

    plot(x, y(idx,:))
end

You could plot the second curve using

plotting_fcn([false true false false])

or

plotting_fcn(2)

[David Barry]

There original way is more robust e.g. if I specify idx of 5 your method falls over. There original method also assumed that they always wanted the first y.

[Andrew Newell]

Strings are still a clumsy way of doing it. Given the revised statement of the problem, I would suggest

function varargout = reporting_GUI(varargin)
  function run_btn_Callback(hObject, eventdata, handles)
      choices = ([1 checkbox1 checkbox2 checkbox3] == 1);
      plt_str(choices)
  end
  function plt_str(choices)
      x1 = [1,2,3,4,5];
      y = [10,20,30,40,50; ...
          20,30,40,50,60; ...
          30,40,50,60,70; ...
          40,50,60,70,80];

        plot(x1,y(choices,:))
    end

Now it's robust. Note that now the first element in choices is always 1, which answers your second objection.

[Andrew Newell]

For completeness, here is how to do it with a string:

eval(['plot(',str,')'])

But before using that solution, see Why avoid the eval function?

Answer 2

[David Barry]

function plotting_fcn(bool1, bool2, bool3)
    x1 = [1,2,3,4,5];
    y1 = [10,20,30,40,50];
    y2 = [20,30,40,50,60];
    y3 = [30,40,50,60,70];
    y4 = [30,40,50,60,70];
    data = y1;
    if(bool1 == 1)
      data = [data; y2];
    end
    if(bool2 == 1)
      data = [data; y3];
    end
    if(bool3 == 1)
      data = [data; y4];
    end 
    plot(x1, data)
end

[David Barry]

I assumed you meant x1 not x.

You also had a typo with bool3 in your function declaration.

[Kellen Madsen]

Right, Thanks David.

This was just a quick example I threw together, the real implementation is much more difficult to bring into this conversation.

My main problem is that I am doing this from a MATLAB GUI and based upon a button press am passing a structure full of parameters. Once these parameters are passed into the function via the struct, they are broken down and then all variables are initialized.

The problem with doing it the way suggested above is that I would need to have those variables already initialized and then create the data variable, which then would be added to my struct and passed in. I would prefer not passing in more data than necessary as these are larger files, but if this is the only way I may be able to make it work.

Regards,

Kellen

[David Barry]

I just went on what you gave and solved the problem in hand. It's not clear from your description exactly what you are trying to do. I suggest including the actual code and an example of the struct you are passing as an input to the plotting function.

[Kellen Madsen]

I have a GUI that takes users input, this is one example of input they may provide, and because of the input they can choose to plot all of the thermocouples, or just a selection of them.

function varargout = reporting_GUI(varargin)

    function run_btn_Callback(hObject, eventdata, handles)

      str = 'x1, [y1';

      if(checkbox1 == 1)
        str = strcat(str, ',y2');
      end

      if(checkbox2 == 1)
        str = strcat(str, ',y3');
      end

      if(checkbox3 == 1)
        str = strcat(str, ',y4');
      end

      str = strcat(str, '];');

      plt_str(str)
  end

function plt_str(str)

    x1 = [1,2,3,4,5];
    y1 = [10,20,30,40,50];
    y2 = [20,30,40,50,60];
    y3 = [30,40,50,60,70];
    y4 = [40,50,60,70,80];

    % HOWEVER I CAN CONVERT str INTO SOMETHING THAT CAN BE PLOTTED. 
    plot(str)
end

This format allows for several different functions to be created and by simply passing the string the selection of variables can be made in the function that is plotting the data, rather than a LARGE amount of data being passed into the function.

Answer 3

[Oran Levi]

function [text] = lines_intersect(str1,str2)

%UNTITLED4 Summary of this function goes here

% Detailed explanation goes here

x=linspace(-10,10)

plot(x,str1,'r-',x,str2,'g-')

plot(,,'r*')

xlabel('x');

ylabel('y');