how to get element from matrix

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ans sobhi
ans sobhi 2019-2-18
评论： Arianna Arianna Clemente 2021-3-24
function btn_forward_Callback(hObject, eventdata, handles)
% hObject handle to btn_forward (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
Th_1 = str2double(get(handles.Theta_1,'string'))*pi/180;
Th_2 = str2double(get(handles.Theta_2,'string'))*pi/180;
Th_3 = str2double(get(handles.Theta_3,'string'))*pi/180;
Th_4 = str2double(get(handles.Theta_4,'string'))*pi/180;
L_1 = 10;
L_2 = 20;
L_3 = 30;
L_4 = 10;
L(1) = Link([0 L_1 0 pi/2]);
L(2) = Link([0 0 L_2 0]);
L(3) = Link([0 0 L_3 0]);
L(4) = Link([0 0 L_4 0]);
Robot = SerialLink(L);
Robot.name = 'anosh';
Robot.plot([Th_1 Th_2 Th_3 Th_4]);
T = Robot.fkine([Th_1 Th_2 Th_3 Th_4]);
handles.Pos_X.string = num2str(floor(T(1,4)));
function Pos_X_Callback(hObject, eventdata, handles)
there is error
Index exceeds matrix dimensions.
Error in ggg>btn_forward_Callback (line 188)
handles.Pos_X.string = num2str(floor(T(1,4)));
Error in gui_mainfcn (line 95)
feval(varargin{:});
Error in ggg (line 42)
gui_mainfcn(gui_State, varargin{:});
Error in
matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)ggg('btn_forward_Callback',hObject,eventdata,guidata(hObject))
Error while evaluating UIControl Callback.
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Adam Danz
Adam Danz 2019-2-20
This suggests that T was not originally a matrix with 4 columns but instead, a structure. When you tried to get data from the 4th "column" of a structure, you got the error. 190220 084433-128.151.171.191 - Remote Desktop Connection.jpg
Arianna Arianna Clemente
Arianna Arianna Clemente 2021-3-24
Hi, have you managed to run also the inverse kinematics?

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回答（1 个）

Adam Danz
Adam Danz 2019-2-20
编辑：Adam Danz 2019-2-25
Here's a summary of the comments under the question so that this question is marked as answered.
The variable "T" is a structure but was being accessed as if it were a matrix.
Here's a replication of the error
T.T1 = magic(4); % a 4x4 matrix stored in field 'T1' of structure "T"
T(1,4)
Index exceeds matrix dimensions. %matlab 2017b
Index in position 2 exceeds array bounds (must not exceed 1). %Matlab 2018a
Here's the solution
T.T1(1,4)
ans =
13

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