MATLAB: Check if variable exists in workspace to plot variable, else generate error

check variableerrorerrordlgexistguiif statementMATLABworkspace

Hi there,
I am having some trouble with checking if a variable exists in the workspace. If the variable exists (which is a structure with time), it should plot the data in my GUI. If the variable does not exist, it should generate an error.
I used this code, however it will always generate an error even if the variable does exist in the workspace. I cannot find what I am doing wrong.
function AmechM_Callback(hObject, eventdata, handles)% Executes on button press in AmechM.
if exist('AmechM','var')
        AmechM = evalin('base','AmechM');
        plot(AmechM.time,AmechM.signals.values);
        xlabel(handles.ax1,'time (s)');
        ylabel(handles.ax1,'Acceleration (rad/s²)');
else
        errordlg('The workspace does not contain any data. Run a simulation first.','Error');
end

Best Answer

replace
    if exist('AmechM','var')
by
    if exist('AmechM','var') == 1
or rather by
    ise = evalin( 'base', 'exist(''AmechM'',''var'') == 1' )
    if ise
since you want to know whether AmechM exists in the base workspace
and read the on-line help on exist and on "scope"
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