[LON-CAPA-users] GeoGebra (Function Plot Response) Problem - Turn off snap to grid

Jon Hall jdh65 at bellsouth.net
Sun Sep 27 22:00:38 EDT 2015

Is there any way to turn off the “snap to grid” feature in the Function Plot Response problems? 

Some of the vector heads/tails that students have to manipulate are so close to certain grid junctions that the vector snaps to the junction, but that moves them to a position that the computer then evaluates as incorrect.

I have tried setting the grid visibility to off, but the snap to feature is still present.

An example of a problematic problem is shown below:

<script type="loncapa/perl">

<startouttext />
a) Amit flies due east from San Francisco (SFO) to Washington, D.C. (IAD), a displacement of &format($IADx,'1f') km. He then flies from Washington to Boston (BOS), a displacement of &format($d2,'1f') km at an angle of &format($theta2,'1f')° west of north. <p />
<li>In the diagram below the black vectors can be moved by grabbing them in the center and they can be adjusted by grabbing the blue dots at either end.</li>
<li>The red vector automatically adjusts itself and you should not try to change its position or length manually.</li>
<li>Move and adjust the SFOtoIAD vector so it originates at SFO and terminates at IAD.</li>
<li>Move and adjust the IADtoBOS vector so it originates at IAD and terminates at BOS.</li>
<li>Notice that the red resultant vector changes as you change the other two vectors.</li>
<li>When you have adjusted the black vectors as described, press the submit button.</li>
<endouttext />

<part id="a">

<functionplotresponse id="11" ymin="-200" xaxisvisible="no" width="450" gridvisible="yes" ymax="1200" height="250" yaxisvisible="no" xmax="6200" xmin="-200">
<plotobject x="0" y="0" label="SFO" />
<plotobject label="IAD" y="0" x="$IADx" />

<plotobject x="$BOSx" y="$BOSy" label="BOS" />
<plotvector taily="800" tailx="2000" tipy="800" tipx="3000" label="SFOtoIAD" />
<plotvector label="IADtoBOS" taily="500" tailx="2000" tipy="500" tipx="3000" />

<drawvectorsum label="Resultant" vectorlist="SFOtoIAD,IADtoBOS" showvalue="yes" tailx="0" taily="0" />
<functionplotvectorrule vector="SFOtoIAD" index="SFOtoIAD" tippoint="IAD" tailpoint="SFO" />
<functionplotvectorrule vector="IADtoBOS" index="IADtoBOS" tippoint="BOS" tailpoint="IAD" />

<functionplotvectorsumrule index="Total" vectors="SFOtoIAD,IADtoBOS" />



<part id="b">
<startouttext />
b) What is the magnitude of Amit's total displacement?
<endouttext />
<numericalresponse format="2f" answer="$dt" unit="km" id="12">
<responseparam description="Numerical Tolerance" type="tolerance" name="tol" default="5%" />

    <textline spellcheck="none" readonly="no" />


Any suggestions would be appreciated.

Jon Hall

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