Dynamically change .txt file name in MATLAB, COMSOL simulation

I have exported code for my COMSOL simulation to MATLAB and I am working on looping through different parameter values for each run of the simulation. At the end of each simulation I need the data to be exported to a file (ideally .csv but it appears I can only do .txt). I need the file name to be updated each time the loop runs.

The problem with the code below is that fname is not recognized as a variable and the file name comes out to be

/Users/marissawhitby/Desktop/C:\Users\jmw\Desktop\Output_Texts\fname

I'm really confused how to do this using COMSOL specific code because I've done similar things in normal MATLAB code in the past.

Any suggestions on how to fix this naming of the .txt file or even how to also get it as a .csv is greatly appreciated.

Note: I've also tried just fname instead of the full file path but that doesn't seem to work either.

Code:

fname = sprintf('Results_E_Field_Iter%d.txt', iter);
model.result.export('data1').set('filename', '/Users/marissawhitby/Desktop/C:\Users\jmw\Desktop\Output_Texts\fname');
model.result.export('data1').set('header', false);
model.result.export('data1').run;

[Rebeka Sultana]

Hello Marissa,

Is that export command is applicable for each loop iteration? I am working on a problem where the output result is posprocessing of data set (some matrix table) from a nested loop. But I am unable to save/export the table result for each iteration in an allocated path I want. Only the first result is being saved with "model.result.table('tbl1').save('Mutual.csv');" comand. Can you help me find out what I am missing here?

Answer 1

[Jan]

fname = sprintf('Results_E_Field_Iter%d.csv', iter);
file  = fullfile('/Users/marissawhitby/Desktop/C:\Users\jmw\Desktop\Output_Texts', fname)
model.result.export('data1').set('filename', file);

Because fname is a variable, using it inside a char vector does not work. So simply use it as a variable.

Are you sure that the file path is correct? It looks neither as Unix nor as Windows.

[Marissa Whitby]

Thank you! The naming worked however now it is refusing to write to the file. I got the error

Java exception occurred:
Exception:
	com.comsol.util.exceptions.FlException: Cannot open file for writing
    Messages:
	Cannot open file for writing.
	- Filename: /Users/marissawhitby/Desktop/C:\Users\jmw\Desktop\Output_Texts/Results_E_Field_Iter2.txt
	- Feature: Data 1

Stack trace:
	at com.comsol.post.export.k.a(SourceFile:183)
	at com.comsol.post.export.g.a(SourceFile:91)
	at com.comsol.post.export.k.execute(SourceFile:93)
	at com.comsol.model.dbmodel.ExportFeatureDb.run(SourceFile:61)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.comsol.bridge.command.b.a(SourceFile:145)
	at com.comsol.bridge.command.b.run(SourceFile:90)
	at com.comsol.bridge.command.i.execute(SourceFile:46)
	at com.comsol.bridge.command.j.d(SourceFile:719)
	at com.comsol.bridge.command.j.a(SourceFile:707)
	at com.comsol.bridge.command.j$3.a(SourceFile:608)
	at com.comsol.bridge.command.j$3.call(SourceFile:1)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
 
>> 

[Marissa Whitby]

Also the file path is for MacOs. I got that part directly from the exported COMSOL model.

[Marissa Whitby]

Nevermind I figured it out thank you very much for your help!! That was very helpful I really appreciate it.

[ferdaous TRIBAK]

Hi Jad;

I exported the comsol simulation code exactly as it is. without any modification. (after saving the comsol simulation in .m format, I opened the file in matlab and run the code without any modification so i can simulated it in matlab and then work on optimization side. ; I got the following errors. what should I do to make it work? what does it mean

can you please help me?

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Error using Ferdaous (line 4630)

Java exception occurred:

Exception:

com.comsol.util.exceptions.FlException: Syntax error in expression

Messages:

Failed to evaluate expression for parameter Fzz.

Syntax error in expression.

- Expression: atan( (1/sqrt(((RT+H)/RT))*((RT+H)/RT))-1))-sqrt(((RT+H)/RT))*((RT+H)/RT))-1) )/pi

- Subexpression: )-sqrt(((RT+H)/RT))* ...

- Position: 43

Stack trace:

at com.comsol.util.classes.exprparser.ExprParser.a(SourceFile:75)

at com.comsol.util.classes.exprparser.ExprParser.a(SourceFile:214)

at com.comsol.util.classes.exprparser.ExprParser.a(SourceFile:126)

at com.comsol.util.classes.exprparser.ExprParser.a(SourceFile:273)

at com.comsol.util.classes.exprparser.ExprParser.a(SourceFile:253)

at com.comsol.util.classes.exprparser.ExprParser.a(SourceFile:241)

at com.comsol.nativeutil.parser.ParseUtil.a(SourceFile:1095)

at com.comsol.nativeutil.parser.ParseUtil.a(SourceFile:1066)

at com.comsol.applapi.variables.am.replaceWithCompleteNames(SourceFile:3499)

at com.comsol.model.applapi.UnitConverter.getUnitExpr(SourceFile:647)

at com.comsol.core.parameter.ParamDatabase.a(SourceFile:967)

at com.comsol.core.parameter.ParamDatabase.set(SourceFile:907)

at com.comsol.core.parameter.ParamDatabase.a(SourceFile:867)

at com.comsol.model.dbmodel.ModelParamDb.addParametersToDatabase(SourceFile:235)

at com.comsol.model.method.ModelMethod.updateParamDatabase(SourceFile:3079)

at com.comsol.core.parameter.ParamDatabase.b(SourceFile:141)

at com.comsol.core.parameter.ParamDatabase.a(SourceFile:116)

at com.comsol.model.method.ParamBaseMethod.updateDependentParamDatabases(SourceFile:340)

at com.comsol.model.method.ModelParamMethod.updateDependentParamDatabases(SourceFile:172)

at com.comsol.model.dbmodel.ParamBaseDb.a(SourceFile:165)

at com.comsol.model.dbmodel.ModelEntityDb.handleEvent(SourceFile:958)

at com.comsol.model.data.EventManager.a(SourceFile:650)

at com.comsol.model.data.EventManager.sendEvent(SourceFile:633)

at com.comsol.model.data.EventManager.a(SourceFile:625)

at com.comsol.model.data.EventManager.a(SourceFile:487)

at com.comsol.model.data.MList.a(SourceFile:122)

at com.comsol.model.data.MList.set(SourceFile:432)

at com.comsol.model.dbmodel.ModelParamDb.a(SourceFile:121)

at com.comsol.model.dbmodel.ModelParamDb.b(SourceFile:1)

at com.comsol.model.dbmodel.ParamBaseDb.a(SourceFile:551)

at com.comsol.model.dbmodel.ParamBaseDb.set(SourceFile:515)

at jdk.internal.reflect.GeneratedMethodAccessor122.invoke(Unknown Source)

at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)

at java.lang.reflect.Method.invoke(Unknown Source)

at com.comsol.bridge.command.c.a(SourceFile:147)

at com.comsol.bridge.command.c.run(SourceFile:90)

at com.comsol.bridge.command.l.c(SourceFile:213)

at com.comsol.bridge.command.l.a(SourceFile:203)

at com.comsol.bridge.command.l$1.run(SourceFile:94)

at com.comsol.util.thread.SuspendableTasks$1.run(SourceFile:111)

at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)

at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)

at java.lang.Thread.run(Unknown Source)

[Jan]

atan((1/sqrt(((RT+H)/RT))*((RT+H)/RT))-1))-sqrt(((RT+H)/RT))*((RT+H)/RT))-1))/pi
%                                        ^

This closing parenthesis is orphaned. The last 3 closing parentheses seems to have no opening counterpart also.

But what is the connection to this thread? Your problem does not concern the question. So please open a new thread.