How to read a numerical value from a static text box?

I tried it like this, but it won't use the value to calculate and plot the sine wave.

function pushbutton2_Callback(hObject, eventdata, handles)

f=num2str(get(handles.text6,'String'));
t=0:0.01:1;
b=sin(2*pi*f*t);
axes(handles.axes1);
plot(b);

This is where I calculate the f, with another pushbutton

function pushbutton1_Callback(hObject, eventdata, handles)
r=handles.edit1;
c=handles.edit2;
f=1/(2*pi*r*c);
set(handles.text6,'String',strcat(num2str(f*1000,2),' Hz'))

[Rik]

For general advice and examples for how to create a GUI (and avoid using GUIDE), have look at this thread.

Answer 1

[Maximilian Schönau]

Did you try str2double instead of num2str? ;)

[Vivien Bartis]

okay, now I don't get the error, but I have still no plot.

Answer 2

[Rik]

You need to strip the unit from the char array. Best practice is to keep numeric fields as pure as possible. With the uifigure-tools it is possible to enforce this during input, but in this case you need to remove it yourself:

function pushbutton2_Callback(hObject, eventdata, handles)
f=get(handles.text6,'String');%retrieve value from text field
f=strrep(f,'Hz','');%remove unit
f=num2str(f);%convert to value
t=0:0.01:1;
b=sin(2*pi*f*t);
plot(t,b,'Parent',handles.axes1);
%    ^^ are you sure you don't want this instead of only b?
end