Check if variable exists in workspace to plot variable, else generate error
1,541 views (last 30 days)
Show older comments
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
2 Comments
per isakson
on 9 Jan 2015
"exists in the workspace"   which workspace, that of the callback function or the base?
Accepted Answer
per isakson
on 9 Jan 2015
Edited: per isakson
on 9 Jan 2015
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"
8 Comments
Moritz Plinke
on 14 Feb 2020
Edited: Moritz Plinke
on 14 Feb 2020
I know answer is really late but I struggled on a very similar case. My solution is using the function fieldnames().
contains( fieldnames( variable_to_inspect) , 'sub_variable_name_string' )
To make it suitable and robust for "if", use sum()
sum( contains( fieldnames( variable_to_inspect ) , 'sub_variable_name_string' ) )
More Answers (0)
See Also
Categories
Find more on Loops and Conditional Statements in Help Center and File Exchange
Products
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!