Sunday, August 23, 2009

Moving averages and the CAS calculator

On the fx casio, moving averages were a bit of a doddle.. stick in the values and use the MAV application.

The suggested method for the classpad 330 according to the classpad website is to use spreadsheet mode. This has some disadvantages that I have not been able to overcome with my brief investigation.

To set up a MAV problem, clear the sheet and enter the basic data in columns. To calculate the MAV click on the middle cell of the first series (eg in a 3pt MAV it would be the second cell) and use the Action column to find the mean of the first three data cells. Then copy your mean cell down the column by highlighting the rest of the column using the stylus and then use the edit menu -> paste.

To graph it is a little on the fiddly side. Highlight the data column and the MAV column and press the line graph icon (there are two, it's the first one). Select the graph and go View->Markers to turn off the data markers. Under the Type menu, make sure you have selected Column Series.

This should display the graph.

If you need a line of regression, select the MAV line with the stylus and select an appropriate regression function on the toolbar. The main issue with it is that there is no way to interpolate or extrapolate data (the main thing you wish to do with this sort of data) for predicting data points whilst in spreadsheet mode for the line of regression. It's been fairly frustrating. I can recreate the line of regression for the MAV in "graph and tab" mode and use this but it would be easier just to have a trace mode on the stats graph... oh well...

Here's a link to an index of other CAS calculator posts.

Update 15/09/09: Download v3.04 of the classpad operating system from here. It greatly enhances the ability of spreadsheet mode to perform regression in spreadsheet mode. You will need to register and login before downloading it.  It's quite a neat trick to click on the line of regression, copy it and then paste the formula onto the spreadsheet at the the bottom of the y column.  Modify the formula such that x becomes a cell reference (eg A2) and viola - an alternate to trace for predicting y values.

:-)

6 comments:

  1. A different method for dealing with moving averages on the Casio classpad is to input the collected data (Ie. time and moving averages) into separate columns in the 'statistics' section of the CAS calculator. To the best of my knowledge, moving averages would have to be calculated by hand, but after reading your post I think this is an easier process, especially in regards to graphing.

    To graph your data in statistics mode, under 'calc' click on 'linear regression' (or whichever is appropriate). A small screen will appear with the equation of the line of regression as well as the correlation coefficient before graphing the data with the line of regression already in place. You can interpolate and extrapolate the data easily (under analysis -> trace) if you have the right domain. Zoom out of the graph to extrapolate data.

    This is just an alternative method in handling moving averages.

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  2. I did consider this and even looked at Mat->list and list->mat functions to copy the data across and back.

    I did do the exercise with spreadsheet mode with my students today and they did seem to get it, combining it with CMA (as this allowed to go back to single units per line and generate a regression line) and residuals seem to work ok, as long as they had a firm understanding of what the intention of the Saddler exercises were.

    I used an icecream shop to look at how residuals could be used to predict ice cream requirements and the linear regression equation found in spreadsheet mode could be manually entered under graph and tab mode.

    I suppose I was just disappointed that it actually got harder going from the fx to the CAS calculator and that it required manual entry in stats mode to do some fairly simple. I suppose I should get out the programming manual and code something up, but I imagine it's around the corner anyway.

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  3. There is supposably a MAV program for the classpads does anyone no where i can get it? my maths teacher said he got his from the casio website but i cant seem to find it on there any help?

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  4. I haven't seen it yet.. the old fx MAV programme was very good for solving MAV problems. Another teacher at our school says he ported them across easily last year, but we've never been able to find out where or how it did it.

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  5. Just do it by hand

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  6. I'd agree but in too many cases it takes too long. You won't get the question finished in the time allotted compared to a student that knows how to do it with the calculator.

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