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Graphing with GUI

Using

x=-10:0.1:10
f=x+2

in basic m-file works fine.

But now I am trying to draw a plot using GUI, and by inputing a function. It gives me bunch of errors. Could anyone explain how I can give values to the y when I have the range of x set?

% --- Executes on button press in zimet.
function zimet_Callback(hObject, eventdata, handles)
% hObject    handle to zimet (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
x=-10:0.1:10;
f=inline(get(handles.vdj,'string'))
y(x)=f

axes(handles.axes)
plot(x,y)







color=get(handles.listbox, 'value')
switch color
    case 2
       set(plot(x,y),'color', 'r')
    case 3
        set(plot(x,y),'color', 'g')
    case 4
        set(plot(x,y),'color', 'b')
end

style=get(handles.popupmenu, 'value')
switch style
    case 2
        set(plot(x,y), 'linestyle','--')
    case 3
        set(plot(x,y), 'linestyle','-.')
    case 4
        set(plot(x,y), 'linestyle',':')
end
rezgis=get(handles.grid, 'value')
switch rezgis
    case 1
        grid on
    case 2
        grid off
end

Answer*

Notice that according to the [inline function documentation](https://uk.mathworks.com/help/matlab/ref/inline.html) this function will be removed in future release; you can use, instead, `anonymous functions` (see below).

The `inline` function require, as input a string of characters while the `get` function returns the text of the edit box as a `cellarray`, therefore you have to convert it using the `char` function.

Also, once you have generated the `inline` object, it is you function, so you have to use it directly.

**Using inline**

You have to change your code this way:

    x=-10:0.1:10;
    % f=inline(get(handles.vdj,'string'))
    % y(x)=f
    f=inline(char(get(handles.vdj,'string')))
    y=f(x)
    axes(handles.axes)
    ph=plot(x,y)

**Using an anonymous function**

You can achieve the same result by using [anonymous functions](https://uk.mathworks.com/help/matlab/matlab_prog/anonymous-functions.html) this way:

    x=-10:0.1:10;
    % Get the function as string
    f_str=char(get(handles.vdj,'string'))
    % add @(x) to the string you've got
    f_str=['@(x) ' f_str ];
    % Create the anonymous function
    fh = str2func(f_str)
    % Evaluate the anonymous function
    y=fh(x)
    
    axes(handles.axes)
    ph=plot(x,y)

**Edit**

You can fix the problem with the setting of the line color and style this way:

- modify the call to `plot` by adding the return value (it is the handle to the plot (see above: `ph=plot(x,y)`)
- chance the calls to `set` by replacing the call to plot with the handle of the plot itself (the `ph` variable as above)

So, to change the color and the line style, in your `switch` section:

    set(ph,'color','r')
    set(ph,'linestyle','--')


Hope this helps,

Qapla'

Edit Summary*

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Thanks ! But if I , for example, type in x^2 , it doesnt work again. I must get it to understand it as .^2 I assume. is there a way of doing that instead of typing it myself ?

Rihards
– Rihards

2017-04-01 15:41:25 +00:00
Commented Apr 1, 2017 at 15:41
I think the only way is you to take care of define the function in the textbox in the right way. You can add, in the callback some code to perform some checks on the string in order to validate it.

il_raffa
– il_raffa

2017-04-01 15:57:07 +00:00
Commented Apr 1, 2017 at 15:57
I've also edited the answer: the inline function will be removed in future release of MatLab. I've added a posible solution using anonymous functions.

il_raffa
– il_raffa

2017-04-01 15:59:38 +00:00
Commented Apr 1, 2017 at 15:59
Thanks! If you dont mind.. perhaps you could also know why using listboxes, popupmenus etc.. I have set one to set the style of the graph, the other for color. The last one overwrites the first one. For example I check color green and dotted style. It will be blue (default) and dotted. How can I stop it from overwriting ?

Rihards
– Rihards

2017-04-01 16:16:31 +00:00
Commented Apr 1, 2017 at 16:16
It is not clear what you mean with "overwritting". You should post that part of your code otherwise it is very difficult to identify the possible errors.

il_raffa
– il_raffa

2017-04-01 16:32:34 +00:00
Commented Apr 1, 2017 at 16:32

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Graphing with GUI

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