MATLAB: Doc Command Cannot Open Documentation Well

documentationhelp

Hi, everyone!
I have an issue with doc command.
So, when I use the following command to call a documentation page on a certain function (for instance, find) like this:
doc find
Instead of opening a window of a documentation page on find function, it calls the MATLAB File Help.
While
doc
will open the desired Documentation Main Page, but when I searched for the function, it failed to brought up results. Instead, the command window displayed some errors:
Exception in thread "com.mathworks.mlwidgets.help.messages.HelpSystemMessageChannel Message Channel Thread": java.lang.NullPointerException
	at com.mathworks.search.lucene.LuceneIndexUtils.indexContainsField(LuceneIndexUtils.java:75)
	at com.mathworks.helpsearch.DocSearchEngineFactory.createAutoSearchEngine(DocSearchEngineFactory.java:64)
	at com.mathworks.help.helpui.search.DocSearchHandler.doSearch(DocSearchHandler.java:58)
	at com.mathworks.help.helpui.search.DocSearchHandler.doSearch(DocSearchHandler.java:51)
	at com.mathworks.mlwidgets.help.messages.search.DocSearchMessageHandler.handleSearch(DocSearchMessageHandler.java:54)
	at com.mathworks.mlwidgets.help.messages.search.DocSearchMessageHandler.handle(DocSearchMessageHandler.java:48)
	at com.mathworks.mlwidgets.html.messages.BrowserMessageSubscriber$HelpMessageRunnable.run(BrowserMessageSubscriber.java:110)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
…
When I looked at the Preferences > Help, I found that the Documentation Location is chosen as 'Locally Installed' as a default.
Thus, I changed the preference to 'Web, on mathworks.com (Internet connection required)' as well as selected all products, also tried both choices in Quick Help Display Section.
After those trials, I got
doc
works well and are able to search for functions documentation as usual.
However,
doc find
still open the MATLAB File Help instead of the Documentation page.
…
This has not been an issue in the past. It is only after I reinstalled to add 'System Identification Toolbox' that the problem arises.
Could anyone tell me how to solve this issue? I really enjoy the tidy and clean MATLAB Documentation, so this problem is quite disturbing for me.
As for me, I use MATLAB R2020a, on Windows 7 64-bit, with unrestricted internet access.

Best Answer

Hi, everyone.
This problem has been resolved after I reinstall MATLAB R2020a Update 5.
As I tried to uninstall MATLAB using Control Panel, I got an error of missing file in helpsearch folder for Image Processing Toolbox.
I don't know how these files are suddenly lost after I add System Identification Toolbox, but I think this issue may have some connection to the failure of MATLAB Documentation search.
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