Checking memory usage by Igor

It would be helpful to know what version of Igor you are using. My guess is Igor Pro 6.xx, 32-bit version. If you were running the 64-bit version of Igor Pro 8, you would probably not need to do any memory checking.

The only reliable way to check this is to try to create a wave of a certain size. For example:

Function CheckMemoryAvailability(numberOfMegabytes)	// Returns 0 for success, non-zero for failure
	Variable numberOfMegabytes
	
	Variable numBytes = 1048576*numberOfMegabytes
	Make/B/U/O/N=(numBytes)/FREE temp
	Variable err = GetRTError(1)		// Get error if any, and clear it
	return err
End

I would check the free memory at good points, and if that is too low do your cleanup. I've posted https://www.wavemetrics.com/code-snippet/get-free-memory-gb for getting the free memory.

In Igor 7 and later, the string returned by WaveInfo contains the size of the wave in the SIZEINBYTES keyword. You could walk your data tree to calculate the total amount of data used by waves in your experiment. Or, if the experiment is saved on disk, you could look at the size of the file itself with GetFileFolderInfo. Igor experiments don't compress the data contained in the experiment, so the size of an experiment file should roughly correlate with the amount of memory used when an experiment is loaded.

With SIZEINBYTES keyword, I made a code for folder size calculations.

Function SLP_Util_FolderTotalSizeMBytes(FolderName,Print_Flg)
	//CREATED: 09.02.2021
	//DESCRIPTIONs: Calculate folder size (all waves combined) including wave in subfolders.
	String FolderName //Full path of a folder to check **Without ":" at the end
	Variable Print_Flg //Show size of each subfolders
	
	String List_FoldersInFolder=""
	String CurrentFolder=GetDataFolder(1)
	
	SetDataFolder $(FolderName+":")
	List_FoldersInFolder=StringByKey("FOLDERS",DataFolderDir(1),":")
	
	String SubFolder_FName=""
	
	Variable i=0
	Variable TotalSize=SLP_Util_FolderWaveSizeMBytes(FolderName,0) 
	If (Print_Flg)
		Print "Waves in "+FolderName+": "+num2str(TotalSize)+" MBytes" //Show combined size of all waves in the specified folder.
	EndIf
	Variable SubFolderSize=0
	
	For (i=0;i<itemsinlist(List_FoldersInFolder,",");i+=1)
		SubFolder_FName=FolderName+":"+StringFromList(i,List_FoldersInFolder,",")
		//TotalSize+=SLP_Util_FolderWaveSizeMBytes(SubFolder_FName,0) //All waves in this Subfolder
		SubFolderSize=SLP_Util_FolderTotalSizeMBytes(SubFolder_FName,0) //Recursive - look inside the subfolder
		TotalSize+=SubFolderSize
		If (Print_Flg)
			Print SubFolder_FName+": "+num2str(SubFolderSize)+" MBytes"
		EndIf
	EndFor
	
	SetDataFolder $CurrentFolder
	If (Print_Flg)
		Print "Total size = "+num2str(TotalSize)+" MBytes"
	EndIf
	Return TotalSize
End


Function SLP_Util_FolderWaveSizeMBytes(FolderName,Print_Flg)
	//CREATED: 09.02.2021
	//DESCRIPTIONs: Return the total size of all waves in a folder in MBytes (not including waves in subfolders)
	String FolderName //Full path of a folder **Without ":" at the end
	Variable Print_Flg //Flag to print out results
	
	String List_WavesInFolder=""
	String CurrentFolder=GetDataFolder(1)
	setdatafolder $(FolderName+":")
	
	List_WavesInFolder=StringByKey("WAVES",DataFolderDir(2),":")
		
	Variable i=0
	String Name_Wave
	String Info_Wave
	Variable Size_Wave
	Variable Size_Sum=0
	
	For (i=0;i<itemsinlist(List_WavesInFolder,",");i+=1)
		Name_Wave=StringFromList(i,List_WavesInFolder,",")
		Info_Wave=WaveInfo($Name_Wave,0)
		Size_Wave=str2num(StringByKey("SIZEINBYTES",Info_Wave,":"))/10^6 //Size in MBytes
		If (Print_Flg)
			Print Name_Wave+" Size = "+num2str(Size_Wave)+" MBytes"
		EndIF
		Size_Sum+=Size_Wave
	EndFor
	If (Print_Flg)
		Print "Total size = "+num2str(Size_Sum)+" MBytes"
	EndIF
	SetDataFolder $CurrentFolder
	Return Size_SUM
End