Gene,
Maybe you could assign me a student role in your sandbox course?
If I can replicate the "Unable to understand formula" issue for this particular
problem part on one of the LON-CAPA servers I run, I'll then be able to add
some debug code within LON-CAPA, which hopefully will allow me to determine the
cause.
I believe you'll find that your old code would grade a submission of
log10(σ^10) as incorrect, but 10*log10(σ) as correct, whereas the code I
provided would be consistent, in grading both as correct (which was the main
point of my previous reply).
Stuart Raeburn
LON-CAPA Academic Consortium
________________________________________
From: LON-CAPA-users <lon-capa-users-boun...@mail.lon-capa.org> on behalf of
Harding, Gene L <glhar...@purdue.edu>
Sent: Sunday, November 8, 2020 2:23 PM
To: Discussion list for LON-CAPA users
Subject: Re: [LON-CAPA-users] LON-CAPA Error
Hi Stuart,
Thank you for your reply. I tried the code you sent, and it works same as the
old code: correctly when I am logged in as me, but "Unable to understand
formula" when I log in as a student in the sandbox. I guess I am still confused
about why it would interpret a formula correctly in one setting, but not in the
other...
BR,
Gene L. Harding, PE
Associate Professor of ECET
-----Original Message-----
From: LON-CAPA-users <lon-capa-users-boun...@mail.lon-capa.org> On Behalf Of
Raeburn, Stuart
Sent: Saturday, November 7, 2020 2:36 PM
To: Discussion list for LON-CAPA users <lon-capa-users@mail.lon-capa.org>
Subject: Re: [LON-CAPA-users] LON-CAPA Error
Gene,
In a formularesponse item, a student's submission will be checked for
correctness using the maxima CAS, unless sample points were specified in the
formularesponse tag (in which case CAPA is used to check for correctness via
sampling; note: ó is not supported as a variable name in this older
sample-based checking).
The log() function is available in maxima for natural logs, but log10() is not
available, by default.
If students will be submitting answers that include log10() then one approach
would be to call a preprocessor routine which would use a call to
&cas('maxima') to convert the log10(ó) in the submitted expression to natural
logs, i.e., convert log10(ó) to log(ó)/log(10), before comparison with the
computer's answer. Note: in this case the "computer's answer" would need to be
expressed using natural logs.
Accordingly, the script block would contain:
$radarRCS = "+10*log(ó)";
$radarRCS2 = "+10*log(ó)/log(10)";
sub convertlogten {
($answer)=@_;
$expr = 'log10(x) := log(x) / log(10); '.$answer;
$answer = &cas('maxima',$expr);
return $answer;
}
and the formularesponse item would be:
<formularesponse preprocess="convertlogten">
<answergroup type="ordered">
<answer name="log" type="ordered">
<value>$radarRCS</value>
</answer>
<answer name="log10" type="ordered">
<value>$radarRCS2</value>
</answer>
</answergroup>
<textline addchars="ó" size="25" />
</formularesponse>
This change is necessary so that if a student submits an answer of:
log10(ó^10)
this will be graded as correct (i.e., for answer name: log10), as it is
equivalent to 10*log10(ó), which would then be similar to the current behavior
if a student submits an answer of:
log(ó^10)
(i.e., for answer name: log) which is graded as correct as it is equivalent to
10*log(ó)
Note in the preview, displayed below the textbox used to enter an answer, when
log10 is typed, the previewer actually displays the 10 as a subscript.
Stuart Raeburn
LON-CAPA Academic Consortium
________________________________________
From: LON-CAPA-users <lon-capa-users-boun...@mail.lon-capa.org> on behalf of
Harding, Gene L <glhar...@purdue.edu>
Sent: Thursday, November 5, 2020 11:19 AM
To: Discussion list for LON-CAPA users
Subject: [LON-CAPA-users] LON-CAPA Error
Hi,
I am getting an error I don't remember seeing before with a formula response
problem that takes a Greek letter as part of the formula. The odd thing is that
it works fine for me, whether in student or course coordinator mode, but not
for the students. I have been able to recreate the error by logging in as a
student to a Test course and doing the problem from there. The first time I
submitted a response it took 20-30 seconds to process, and gave a timeout
error. Subsequent submissions appear to process much faster, and gave an
"Unable to understand formula" error. It is set up to take either of two
formulas for the answer.
Here are the perl script formula definitions:
$radarRCS = "+10*log(ó)";
$radarRCS2 = "+10*log10(ó)";
This is the formula response code:
<formularesponse id="14">
<answergroup type="ordered">
<answer name="log" type="ordered">
<value>$radarRCS</value>
</answer>
<answer name="log10" type="ordered">
<value>$radarRCS2</value>
</answer>
</answergroup>
<textline addchars="ó" size="25" />
</formularesponse>
This approach works fine for the two preceding problem parts, but they do not
use the "addchars" modifier with a Greek letter.
Has anyone seen this error before and have an idea of what causes it?
Best regards,
Gene L. Harding, PE
Associate Professor of ECET
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