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fixed parameters for Data Tool Autofit post and replies

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fixed parameters for Data Tool Autofit - October 27 at 11:15:AM
Wes Loewer
1 Posts

First of all, thank you for such a great program.  It is well used at our school.

We are using the Data Tool's Fit Builder to build equations for use with the Autofit feature.  For example, if we video a beachball dropping, the first quarter second or so should be fairly parabolic, so if we select Parabola, we can get the value of g from the A parameter.

Now we want to look at the full drop of 2-3 seconds in which air drag is no longer negligible.  Now we're using Fit Builder to enter equations

y=ho+g/sqr(k)*(1-exp(-k*(t+to)))-g*(x+to)/k
or
y=ho-ln(cosh(sqrt(k*g)*(t+to)))/k

which have parameters k, g, ho, and to.

We'd like to use the Autofit feature for these, but we need to keep the value of g fixed to what we found earlier from the Parabola.  Is there any way for Autofit to only use the other 3 parameters and leave g fixed?

My workaround is to manually edit the equation in Fit Builder, putting in the numeric value in place of g, but it would be much better to have something like check-boxes next to each parameter in Data Tool to indicate which parameters are to be varied by Autofit and which are to remain fixed.

Thank you once again.

Wes Loewer
Rosslyn Academy
Nairobi, Kenya


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