MATLAB: ()-indexing must appear last in an index expression What is the mistake? method gauss jordan gui

matlab gui

function pushbutton6_Callback(hObject, eventdata, handles)
set(handles.pushbutton1, 'value');
    u=1;
set(handles.pushbutton3, 'value');
    u=2
set(handles.pushbutton4, 'value');    
    u=3
switch u
    case 1
m=[str2double(get(handles.edit3,'string')) str2double(get(handles.edit4,'string'))(str2double(get(handles.edit9,'string'))); str2double(get(handles.edit10,'string')) str2double(get(handles.edit11,'string')) str2double(get(handles.edit15,'string'))];
    case 2
m=[str2double(get(handles.edit3,'string')) str2double(get(handles.edit4,'string')) str2double(get(handles.edit6,'string')) (str2double(get(handles.edit9,'string'))); str2double(get(handles.edit10,'string')) str2double(get(handles.edit11,'string')) str2double(get(handles.edit12,'string')) (str2double(get(handles.edit15,'string'))); str2double(get(handles.edit16,'string')) str2double(get(handles.edit17,'string')) str2double(get(handles.edit18,'string')) str2double(get(handles.edit21,'string')) ];
    case 3
      case 4
      otherwise
      x=0
  end
  if all(size(m)==[2,3])
     h=1
  else
     if all(size(m)==[3,4])
         h=2
     else
         if all(size(m)==[4,5])
             h=3
         else
             if all(size(m)==[5,6])
                h=4
   end
         end
     end
  end
  switch h
      case 1
      m(1,:)=m(1,:)/m(1,1);
      m(2,:)=m(2,:)-(m(2,1))*(m(1,:));
      m(2,:)=m(2,:)/m(2,2);
      m(1,:)=m(1,:)-(m(1,2))*(m(2,:));
      x1=m(1,3)
      x2=m(2,3)
      set(handles.edit35,'string',x1);
      set(handles.edit36,'string',x2);
      case 2
      m(1,:)=m(1,:)/m(1,1);
      m(2,:)=m(2,:)-(m(2,1))*(m(1,:));
      m(3,:)=m(3,:)-(m(3,1))*(m(1,:));
      m(2,:)=m(2,:)/m(2,2);
      m(3,:)=m(3,:)-(m(3,2))*(m(2,:));
      m(3,:)=m(3,:)/m(3,3);
      m(2,:)=m(2,:)-(m(2,3))*(m(3,:));
      m(1,:)=m(1,:)-(m(1,3))*(m(3,:));
      m(1,:)=m(1,:)-(m(1,2))*(m(2,:));
      x1=m(1,4)
      x2=m(2,4)
      x3=m(3,4)
      set(handles.edit35,'string',x1);
      set(handles.edit36,'string',x2);
      set(handles.edit37,'string',x3);
      case 3
          x=3
      case 4
          x=2
      otherwise
          x=32
    end
matlab says that this is my mistake
m=[str2double(get(handles.edit3,'string')) str2double(get(handles.edit4,'string'))(str2double(get(handles.edit9,'string'))); str2double(get(handles.edit10,'string')) str2double(get(handles.edit11,'string')) str2double(get(handles.edit15,'string'))];

Best Answer

You can't do the following:
str2double(get(handles.edit4,'string'))(str2double(get(handles.edit9,'string')));
Did you mean to add a space between the terms? If not and you want to access the nth index of this variable, keep reading.
Unlike other languages like JAVA, you can't immediately take the output of str2double and find the value at the nth index. You need to use a temporary variable to do this kind of indexing. See this example:
a = {'1' '2' '3'}
b = '2'
c = str2double(a)(str2double(b)) % Error: ()-indexing must appear last in an index expression.
temp = str2double(a);
c = temp(str2double(b));  %no error. this works.
In your case, any string that will return a matrix should be stored in a temporary matrix.
temp  = str2double(get(handles.edit4,'string'))
value = tempMat(str2double(get(handles.edit9,'string')));
If you have to extract a value using 2 edit text boxes frequently, consider making a simple function like this:
function Value = getValue(Handle1, Handle2)
Values = str2double(get(Handle1, 'string'));
Value = Values(str2double(get(Handle2, 'string')));
And whenever you want to get a value from a edit text box based on the index value of another text box, do this:
getValue(handles.edit4, handles.edit9)
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