Undefined function or variable 'isempty'.

Hello all, I'm using version 2016a and have encountered some behaviour I've never seen before. I'm trying to check an excel spreadsheet to see if an entry already exists for a given serial number before adding a new entry. The problem section is:

recordsTable = readtable(FILE_ADDRESS, 'Sheet', systemSheet, 'Range', 'A:I'); % This reads in the data in a table
existingRecord = find(recordsTable.SerialNumbers == projectNum); % This finds any entries which match a given numerical value
if isempty(existingRecord) % This returns the error: Undefined function or variable 'isempty'.
    ...
end

I've used breakpoints to check and existingRecord is empty when isempty is called on it. Indeed, if I place a breakpoint on the problem line and then call isempty(existingRecord) from the command line instead of letting the script continue it works perfectly and returns a 1 as expected. Running each line individually from the command line also works and returns a 1 as expected. It is only when used as part of a script that MATLAB refuses to recognize isempty, despite it being a default function.

I have checked and isempty is on the MATLAB path as it should be. It is included as a built-in function in version 2016a, and my license is current. I've triple checked my spelling of all function and variable names and have spent several hours googling what could be wrong to no avail. No part of my code alters the path, and I'm not trying to use isempty or any variation thereof as a variable name. Any advice would be appreciated as at this point I have no idea why isempty seems to be unusable in a script, despite several hours of googling and reading documentation.

[Torsten]

Do you get something unexpected from the command

which -all isempty

built-in (/MATLAB/toolbox/matlab/elmat/isempty)
built-in (/MATLAB/toolbox/matlab/elmat/@double/isempty)                             % double method
built-in (/MATLAB/toolbox/matlab/elmat/@int16/isempty)                              % int16 method
built-in (/MATLAB/toolbox/matlab/elmat/@int32/isempty)                              % int32 method
built-in (/MATLAB/toolbox/matlab/elmat/@int64/isempty)                              % int64 method
built-in (/MATLAB/toolbox/matlab/elmat/@int8/isempty)                               % int8 method
built-in (/MATLAB/toolbox/matlab/elmat/@logical/isempty)                            % logical method
built-in (/MATLAB/toolbox/matlab/elmat/@single/isempty)                             % single method
built-in (/MATLAB/toolbox/matlab/elmat/@uint16/isempty)                             % uint16 method
built-in (/MATLAB/toolbox/matlab/elmat/@uint32/isempty)                             % uint32 method
built-in (/MATLAB/toolbox/matlab/elmat/@uint64/isempty)                             % uint64 method
built-in (/MATLAB/toolbox/matlab/elmat/@uint8/isempty)                              % uint8 method
isempty is a built-in method                                                        % string method
isempty is a built-in method                                                        % dictionary method
/MATLAB/toolbox/matlab/codetools/@mtree/isempty.m                                   % mtree method
/MATLAB/toolbox/matlab/datatypes/categorical/@categorical/isempty.m                 % categorical method
/MATLAB/toolbox/matlab/datatypes/tabular/@tabular/isempty.m                         % tabular method
/MATLAB/toolbox/matlab/datatypes/datetime/@datetime/datetime.m                      % datetime method
/MATLAB/toolbox/matlab/datatypes/duration/@duration/duration.m                      % duration method
isempty is a built-in method                                                        % connector.internal.LoggerLevel method
isempty is a built-in method                                                        % matlab.internal.lang.capability.Capability method
isempty is a built-in method                                                        % matlab.lang.OnOffSwitchState method
isempty is a built-in method                                                        % containers.Map method
/MATLAB/toolbox/matlab/lang/+matlab/+mixin/@Scalar/Scalar.m                         % matlab.mixin.Scalar method
/MATLAB/toolbox/matlab/indexing/+matlab/+mixin/+indexing/@RedefinesParen/isempty.m  % matlab.mixin.indexing.RedefinesParen method
isempty is a built-in method                                                        % matlab.internal.reference.property.RefEntityType method
isempty is a built-in method                                                        % matlab.internal.reference.api.EntityPrecision method
isempty is a built-in method                                                        % matlab.internal.reference.property.DeprecationStatus method
isempty is a built-in method                                                        % matlab.internal.reference.property.FunctionType method
isempty is a built-in method                                                        % matlab.internal.reference.api.EntityCaseSensitivity method
isempty is a built-in method                                                        % mf.zero.meta.Language method
isempty is a built-in method                                                        % dig.config.CommandType method
isempty is a built-in method                                                        % dig.config.HorizontalAlignment method
isempty is a built-in method                                                        % dig.model.DisplayState method
isempty is a built-in method                                                        % dig.model.EventDataType method
isempty is a built-in method                                                        % dig.model.FunctionType method
isempty is a built-in method                                                        % dig.model.ValidInBdType method
isempty is a built-in method                                                        % dig.model.ViewMode method
isempty is a built-in method                                                        % simulink.FindSystemTask.Status method
isempty is a built-in method                                                        % Simulink.data.adapters.AdapterDiagnostic method
isempty is a built-in method                                                        % Simulink.data.adapters.ChangeType method
isempty is a built-in method                                                        % sl.data.adapter.AdapterType method
isempty is a built-in method                                                        % sl.data.srccache.CacheUpdateResult method
isempty is a built-in method                                                        % sl.data.srccache.cachemgr.CacheStatus method
isempty is a built-in method                                                        % sl.data.srccache.cachemgr.SourceFileStatus method
isempty is a built-in method                                                        % slid.SourceIssue method
isempty is a built-in method                                                        % slid.broker.SourceManagerSourceKind method
isempty is a built-in method                                                        % slid.broker.SourceStatus method
isempty is a built-in method                                                        % dastudio_util.cooperative.AsyncFunctionRepeaterTask.Status method
isempty is a built-in method                                                        % coderdictionary.data.AccessFunctionSignaturesEnum method
isempty is a built-in method                                                        % coderdictionary.data.AccessInterfaceEnum method
isempty is a built-in method                                                        % coderdictionary.data.AccessModeEnum method
isempty is a built-in method                                                        % coderdictionary.data.AllowedAccessEnum method
isempty is a built-in method                                                        % coderdictionary.data.DataAccessEnum method
isempty is a built-in method                                                        % coderdictionary.data.DataAccessTypeEnum method
isempty is a built-in method                                                        % coderdictionary.data.DataInitEnum method
isempty is a built-in method                                                        % coderdictionary.data.DataInstantiationEnum method
isempty is a built-in method                                                        % coderdictionary.data.LatchingModeEnum method
isempty is a built-in method                                                        % coderdictionary.data.PlacementEnum method
isempty is a built-in method                                                        % coderdictionary.data.ScopeEnum method
isempty is a built-in method                                                        % coderdictionary.data.StatementsSurroundEnum method
isempty is a built-in method                                                        % coderdictionary.data.StatusEnum method
isempty is a built-in method                                                        % matlab.unittest.Verbosity method
isempty is a built-in method                                                        % matlab.unittest.internal.fixtures.FolderScope method
isempty is a built-in method                                                        % matlab.internal.timer.CallBackTypeEnum method
isempty is a built-in method                                                        % matlab.internal.timer.BusyModeEnum method
isempty is a built-in method                                                        % matlab.internal.timer.ExecutionModeEnum method
/MATLAB/toolbox/nnet/deep/+deep/+internal/+recording/@RecordingArray/isempty.m      % deep.internal.recording.RecordingArray method
/MATLAB/toolbox/matlab/bigdata/@tall/isempty.m                                      % tall method
/MATLAB/toolbox/matlab/timeseries/@tscollection/isempty.m                           % tscollection method
/MATLAB/toolbox/curvefit/curvefit/@fittype/isempty.m                                % fittype method
/MATLAB/toolbox/finance/ftseries/@fints/isempty.m                                   % fints method
/MATLAB/toolbox/ident/ident/@iddata/isempty.m                                       % iddata method
/MATLAB/toolbox/ident/idobsolete/@idarx/isempty.m                                   % idarx method
/MATLAB/toolbox/ident/nlident/@idnlgrey/isempty.m                                   % idnlgrey method
/MATLAB/toolbox/mpc/mpc/@mpc/isempty.m                                              % mpc method
/MATLAB/toolbox/parallel/gpu/@gpuArray/isempty.m                                    % gpuArray method
/MATLAB/toolbox/parallel/lang/@Composite/isempty.m                                  % Composite method
/MATLAB/toolbox/parallel/parallel/@distributed/isempty.m                            % distributed method
/MATLAB/toolbox/parallel/parallel/@codistributed/isempty.m                          % codistributed method
/MATLAB/toolbox/shared/statslib/@dataset/isempty.m                                  % dataset method

Maybe a duplicate of the function made by you ?

[Jan]

Please post a copy of the complete error message.

[KG]

Torsten, I don't know how that would have happened. I've never knowingly duplicated any function and I've never used isempty as a function name. Furthermore this script, including this problem line, was working just fine yesterday and earlier today and I haven't created any new functions, or touched any toolboxes since.

built-in (C:\Program Files\MATLAB\R2016a\toolbox\matlab\elmat\isempty)

C:\Program Files\MATLAB\R2016a\toolbox\matlab\datatypes\@table\isempty.m % table method

C:\Program Files\MATLAB\R2016a\toolbox\matlab\codetools\@mtree\isempty.m % mtree method

C:\Program Files\MATLAB\R2016a\toolbox\matlab\timefun\@datetime\datetime.m % datetime method

isempty is a built-in method % containers.Map method

C:\Program Files\MATLAB\R2016a\toolbox\matlab\datatypes\@categorical\isempty.m % categorical method

C:\Program Files\MATLAB\R2016a\toolbox\matlab\iofun\@timer\isempty.m % timer method

C:\Program Files\MATLAB\R2016a\toolbox\matlab\timeseries\@tscollection\isempty.m % tscollection method

C:\Program Files\MATLAB\R2016a\toolbox\comm\comm\@gf\isempty.m % gf method

C:\Program Files\MATLAB\R2016a\toolbox\curvefit\curvefit\@fittype\isempty.m % fittype method

C:\Program Files\MATLAB\R2016a\toolbox\distcomp\parallel\@distributed\isempty.m % distributed method

C:\Program Files\MATLAB\R2016a\toolbox\distcomp\parallel\@codistributed\isempty.m % codistributed method

C:\Program Files\MATLAB\R2016a\toolbox\distcomp\lang\@Composite\isempty.m % Composite method

C:\Program Files\MATLAB\R2016a\toolbox\distcomp\gpu\@gpuArray\isempty.m % gpuArray method

C:\Program Files\MATLAB\R2016a\toolbox\finance\ftseries\@fints\isempty.m % fints method

C:\Program Files\MATLAB\R2016a\toolbox\ident\ident\@iddata\isempty.m % iddata method

C:\Program Files\MATLAB\R2016a\toolbox\ident\nlident\@idnlgrey\isempty.m % idnlgrey method

C:\Program Files\MATLAB\R2016a\toolbox\ident\idobsolete\@idarx\isempty.m % idarx method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbc\@xregpointer\isempty.mexw64 % xregpointer method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbc\@xregpointer\isempty.m % xregpointer method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbc\@junit\isempty.m % junit method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbc\@guidarray\isempty.m % guidarray method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbcdata\@cgrules\isempty.m % cgrules method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbcdata\@cgoptcsol\isempty.m % cgoptcsol method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbcdata\@cgoppoint\isempty.m % cgoppoint method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbcdata\@cgcaloutput\isempty.m % cgcaloutput method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbcdesign\@des_constraints\isempty.m % des_constraints method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbcexpr\@cgvariable\isempty.m % cgvariable method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbcexpr\@cgnormfunction\isempty.m % cgnormfunction method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbcexpr\@cgnormaliser\isempty.m % cgnormaliser method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbcexpr\@cgmswitchexpr\isempty.m % cgmswitchexpr method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbcexpr\@cgmodexpr\isempty.m % cgmodexpr method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbcexpr\@cglookuptwo\isempty.m % cglookuptwo method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbcexpr\@cgfuncexpr\isempty.m % cgfuncexpr method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbcexpr\@cgfeature\isempty.m % cgfeature method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbcexpr\@cgexpr\isempty.m % cgexpr method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbclayouts\@xregcontainer\isempty.m % xregcontainer method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbcmodels\@xregcovariance\isempty.m % xregcovariance method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbctools\@sweepsetfilter\isempty.m % sweepsetfilter method

C:\Program Files\MATLAB\R2016a\toolbox\mbc\mbctools\@sweepset\isempty.m % sweepset method

C:\Program Files\MATLAB\R2016a\toolbox\mpc\mpc\@mpc\isempty.m % mpc method

C:\Program Files\MATLAB\R2016a\toolbox\shared\statslib\@dataset\isempty.m % dataset method

[KG]

Jan, the complete error is:

Undefined function or variable 'isempty'.

Error in controlDocUpdate (line 247)

if isempty(existingRecord)

That's all it gives me.

[Walter Roberson]

Do you have a variable named isempty at any point? Possibly accidentally assign to it?

[KG]

Walter, I don't know exactly why this worked, but I think you have inadvertently helped me solve it. I didn't have isempty assigned as a variable anywhere, but while I ctrl-f'd to double check I noticed that in a completely different if statement it was written as

isempty{existingRecord}

instead of

isempty(existingRecord)

Switching to parentheses instead of curly braces did something and now it works again. My (admittedly very limited) understanding is that culy braces only tell matlab that it's a cell array so I have no idea why that made it so that MATLAB couldn't recognize the function in a completely different part of the script, but it's working as intended now. Thanks!

[Walter Roberson]

When matlab saw {} in the code it deduced that isempty must be a variable, and so it does not search the path looking for it as a function.