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

2,061 次查看（过去 30 天）
Maarten
Maarten 2015-1-9
评论： Alex Morgan 2022-8-16
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

请先登录，再回答此问题。

采纳的回答

per isakson
per isakson 2015-1-9
编辑：per isakson 2015-1-9
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 个评论
显示 6更早的评论
Moritz Plinke
Moritz Plinke 2020-2-14
编辑：Moritz Plinke 2020-2-14
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' ) )

请先登录，再进行评论。

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Loops and Conditional Statements 的更多信息

标签

产品

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by